The Invasion (TV story)

The Invasion was the third serial of season 6 of Doctor Who. It featured the Cybermen in what became their established form until Earthshock in 1982.

The Invasion also featured the second appearance of Alistair Gordon Lethbridge-Stewart, now promoted to the rank which became his best known title — Brigadier. It additionally introduced the organisation known as UNIT, as well as the character of Corporal (later Sergeant) John Benton. Behind the scenes, it was the start of Terrance Dicks' record-setting tenure as script editor. Furthermore, it was the final major appearance of the Cybermen until Revenge of the Cybermen in 1975.

Episodes one and four are currently missing from the BBC film archive. However, the two missing episodes were animated for the DVD release in 2006.

Synopsis
The Doctor, Jamie and Zoe return to Earth and become embroiled in the schemes of Tobias Vaughn. They meet up with an old friend, former Colonel and now Brigadier, Lethbridge-Stewart, and some old enemies, the Cybermen.

Episode one
Jamie, Zoe and the Doctor have been all brought back from the Land of Fiction into the TARDIS as it reassembles itself. They find that they are hovering over the dark side of the moon. As they look at the scanners they see something approaching them. They soon realise it is a missile. The Doctor tries to move, but the landing circuit is jammed. The Doctor wrestles with the controls. The missile explodes.

The TARDIS lands with a thud in a field of cows.

Inside the TARDIS, Zoe wonders why they were fired at without any questions being asked. The Doctor wonders if they have encountered whoever fired at them already. They check the scanner, and the sight of cows tells them they are on Earth; the Doctor reckons in the summertime of the 20th century. The TARDIS judders, and the Doctor believes he needs some new parts. He decides to seek out his old friend Professor Travers for help. He takes one of the circuits from the console which causes the lights to fade. They make their way to the exit.

Once outside a lorry draws up. The driver asks if they are "getting out". The Doctor states that they are heading to London. The driver orders them in. The driver looks round nervously as they get in the cab. As he drives off, they are being pursued by two motorbikes. The driver pulls off the road and disappears behind some trees. He stops the lorry and gets out, looking anxiously down the lane before walking off. The Doctor, Jamie and Zoe follow the driver into the undergrowth. The driver suspects that the company is on their trail. When the Doctor queries what he means by the company, he is met with consternation. The Doctor states that they are strangers. The driver wonders how they got into the compound. He explains that the company is International Electromatics, the largest electronics company in the world who have a vast monopoly on the electronics business and huge complexes forming large swathes of land. The driver reckons it's safe to get on the road again.

The lorry approaches a checkpoint. Jamie, Zoe and the Doctor are hidden away in the cab of the lorry. The driver presents his papers and is waved through. Soon after, the driver stops his lorry, and the travellers get out of the back. The driver tells them to get lost before driving off. The Doctor, Jamie and Zoe clamber over a hedge into a field. As they do, the motorbikes pass them by. The guards pull up behind the lorry. As they dismount, one guard opens the lorry to search it. He discovers only milk. The main guard sees the driver's papers whilst the other guard continues his search. The main guard says he wants to take the driver in for questioning. The other guard finds nothing and nods to his partner. The driver states he is not going back to the compound. The guard pulls out his gun. The driver turns to get into the lorry, but the guard shoots him.

The Doctor, Jamie and Zoe are hitch-hiking. A car stops, and the Doctor says they want to go to London. The driver nods, and the Doctor, Jamie and Zoe get into the car.

Once in London, the Doctor and his friends look up Travers' address but on arriving find the name Watkins on the doorbell and there is no answer. They continue ringing until a young model by the name of Isobel answers the door. She explains that Travers is in America with Anne and that her uncle, Professor Watkins, is staying in his house. He is working for International Electromatics and has been away for weeks. The Doctor, seeing his only chance to fix his TARDIS, tries to contact Watkins but comes up against an automated answering service that tells him "Party not available". They decide to go there themselves. Zoe decides to stay as she is enjoying modelling for Isobel.

Two men in a car watch the Doctor and Jamie enter the IE building. They are met by a computer secretary. They, again, ask for Watkins and are, again, told he is not available. They want to speak to someone in authority — but they need an appointment. They need to see someone now — but they're all engaged. It's an emergency — but what kind of emergency? It's a private matter — an emergency cannot be a private matter. The Doctor switches the computer off in frustration. The Doctor and Jamie set off to find another way in.

One of the men in the car takes a photo of the Doctor and Jamie as they explore outside.

A further two men watch them in a video link. One of them flips a switch.

Two glass panels drop down either side of the alleyway that the Doctor and Jamie are in. Gas starts to seep in.

HQ deploy the two men in the car to get the Doctor and Jamie.

The gas has cleared and the guards open the glass panel. As the man prods Jamie with his foot, Jamie grabs it and trips him. The man pulls a gun. A man named Vaughn stops him. Vaughn orders the man with the gun, Packer, to bring the Doctor and Jamie to his office.

Packer is dismissed by Vaughn as soon as he gets to the office. Jamie is initially very aggressive, but the Doctor is passive and apologises for the trespass. Vaughn introduces himself as the director of International Electromatics and states that their friend, Watkins, is very busy and is not available by choice. Jamie is satisfied and begins to ask Vaughan about circuits for the TARDIS. The Doctor kicks him. Vaughn's curiosity is piqued, and he asks how he can help. The Doctor reluctantly hands the circuits over to Vaughn. Vaughn is intrigued and says he'll send them to his workshop. As an apology to Jamie for Packer's rough treatment, he gifts him a disposable transistor radio before dismissing the Doctor and Jamie. Vaughn walks to the desk and flicks a switch. He asks Packer to show the Doctor and Jamie off the premises.

Packer escorts them out. The Doctor believes that Vaughn is not what he seems. He is not blinking at the rate that a normal human should. The Doctor considers him odd, sinister and inhuman.

In his office, Vaughn flicks a switch. A wall tilts back to reveal a piece of complex, alien equipment.

Episode two
As the Doctor and Jamie return from the IE building, they soon discover they are being followed. They start to run.

Back at Travers' house, Zoe is modelling for Isobel. She soon becomes distracted and worried about her friends.

The Doctor and Jamie are chased into an alley where they are caught by a pincer movement and loaded into the cars.

Vaughn shows the circuit given to him by the Doctor to his assistant researcher, Gregory, who is bamboozled by the technology. Vaughn gives him an hour to figure it out. He asks Packer for photos of the Doctor and Jamie.

Zoe has now become so worried about the Doctor and Jamie that she and Isobel set off to find them.

On a mysterious runway, the car into which the Doctor and Jamie were forced boards a plane. They soon find themselves in the hub of a military base where they meet their old friend Colonel Lethbridge-Stewart, now promoted to Brigadier. It has been four years since they last encountered each other in the London Underground, and the Brigadier is now in charge of the United Nations Intelligence Taskforce or UNIT, an international investigatory force. He tells the Doctor that he and Jamie have been being monitored since they left the complex and that he decided to pick them up after they left the IE building. The Brigadier explains that people sometimes enter the IE building, yet never leave.

Zoe and Isobel enter the IE building, seeking the Doctor and Jamie. They try the computer in reception and enquire after them.

Upstairs, Vaughn unveils the alien machinery and asks for information regarding the Doctor. The machine tells him that they are known and hostile. They were encountered on Planet 14 and must be destroyed before the invasion. An alarm interrupts this conversation. Zoe and Isobel are displayed on Vaughn's screens.

The computer receptionist is giving no information to Zoe. Refusing to be beaten, she bamboozles the computer using ALGOL, complex mathematical equations. The machine starts to smoke and eventually explodes.

All this is watched by Vaughn. He calls Packer to bring the two girls up.

Isobel and Zoe start to leave when they are intercepted by Vaughan's guards.

The Brigadier explains to the Doctor that many senior anti-IE figures have entered the IE building and returned completely for their company. Sifting through the photographs, Jamie discovers a photo of the driver that helped them out of the IE complex. The Brigadier explains he was an agent and hasn't been heard of for twelve hours. The Brigadier explains that IE was practically unheard of until they started controlling computer lines and investing in micromonolithic circuits, then Watkins disappeared and UNIT got involved. The evidence is not substantial enough for UNIT to search the IE building, so the Doctor and Jamie are on their own. However, the Doctor is given a transceiver if ever he needs to contact UNIT. The Doctor and Jamie are returned to London.

On their return to London, they discover Travers' house empty. They enter, and the Doctor absentmindedly dismantles the radio that Jamie was given by Vaughn. He discovers micromonolithic circuits that have no place in a radio. They find a note stating that Isobel and Zoe have gone to the IE building. Panicked, they follow them.

Vaughn berates Zoe and Isobel for the destruction of his computer. Vaughn explains that Watkins has started to be uncooperative and that Isobel could be useful in persuading him to work. Zoe and Isobel are seized.

The Doctor and Jamie investigate the outside of the IE building. The Doctor uses the transceiver to check with the Brigadier that Zoe and Isobel actually entered. The Brigadier confirms that they did indeed enter. As they explore, they find a railway line that skirts the back of the building.

Gregory has drawn a blank on the circuits. He is dismissed. Vaughn opens the wall and demands more data on the Doctor. The machine refuses to give more information but just orders the destruction of the Doctor. Vaughn stands up to the machine. He says unless they share information, he will stop helping them. Reluctantly, the machine tells Vaughn that the Doctor has a machine that can help him travel to other planets. Vaughn vows he will destroy the Doctor.

Jamie and the Doctor have sneaked into the building. They witness workers carrying crates far beyond human strength. They sneak away.

An alarm is raised. Packer tells Vaughn that the Doctor and Jamie have been spotted. Vaughn tells Packer not to raise full alert but just to close off the area and that they are to be flushed out using Isobel and Zoe as bait.

As they move around the warehouse, the Doctor and Jamie hear the screams of Zoe and Isobel. Their unconscious forms are being put into crates to be loaded into the return van. Jamie, furious, attacks Packer. Reinforcements are called for, and soon enough Jamie and the Doctor are surrounded by armed guards.

Episode three
Jamie confronts Packer again. Packer goes to hit him, but Vaughn calls him off. Vaughan tells Jamie and the Doctor that Zoe and Isobel were in the building but they left. Jamie protests, but the Doctor calmly asks if they can inspect the containers. Vaughn allows this, but as soon as they all leave to do so, Packer orders the train to leave. Jamie and the Doctor arrive too late. Vaughn suggests that he will accompany them to the factory to do the inspection there.

The Brigadier is worried about the Doctor and Jamie when he receives reports that the two of them plus Vaughn are leaving the building together.

The Brigadier orders them not to be followed and orders one of his subordinates, Jimmy, to go to the factory in a helicopter.

Jimmy watches as Vaughn's car enters the compound. The Brigadier orders Jimmy to hang back as they need to not alert Vaughn's private army, which might put the Doctor and Jamie at risk.

The Doctor and Jamie are led into the factory. Vaughn wants to question the Doctor further on the circuits he showed him. As Vaughn shows the Doctor and Jamie into the office, he suggests to Packer that he should go and see if he can convince Watkins to work.

When the Doctor and Jamie enter Vaughn's office, they are surprised to see that it is exactly the same as his office in London. Vaughn has become suspicious of Zoe and the Doctor's abilities, but he isn't surprised or angry that the Doctor refused to be drawn in. Vaughn promises the Doctor Watkins' help and leaves. Jamie suspects Vaughn, and the Doctor considers him too nice but wonders why he would be offering them Watkins' assistance if he was evil.

Packer is threatening Watkins with harm to Isobel if he doesn't continue working. Watkins considers it a bluff when Vaughn arrives and assures him it is true. He explains that whatever happens Isobel will not be freed, she will just come to harm if Watkins refuses to comply. Watkins reluctantly agrees. Vaughn tells Watkins of the Doctor and Jamie and extends the threat to Isobel to spilling the beans on him.

In the office, the Doctor notices a deep space radio communication system outside. This causes him to be furthermore suspicious of Vaughn. As they look outside, they see Jimmy's helicopter swoop overhead. Packer enters and escorts the Doctor and Jamie into Watkins' presence.

Jimmy reports to the Brigadier that there is no sign of the Doctor or Jamie.

After the Doctor has introduced himself, Watkins says that Travers and Anne told him all about them.

Up in his office, Vaughn tells Packer that the Doctor has been on another planet and has some sort of vessel that he craves. He shows Packer a video screen that shows Watkins, the Doctor and Jamie's conversation.

Jamie begins to talk to Watkins about the TARDIS, but the Doctor stifles him. He is aware they are being bugged. He puts a scrambler on the machine.

Vaughn checks all the other cameras — they are all functioning. He realises that the Doctor is quite an adversary and says it is no surprise his allies fear him. Vaughn has vowed not to destroy the Doctor until he knows more of his machine.

Left alone, Watkins says he is working on a machine called the Cerebration Mentor, a teaching machine. The Doctor tells Watkins about the involvement of UNIT. Watkins says he has no knowledge of Vaughn's plans and thinks he wants complete control of the electronics industry of the world. The Doctor believes he has bigger aspirations than that. Jamie hears someone coming. The Doctor goes for the scrambler, but Vaughn enters and removes it first. Vaughn tells the Doctor that they will make him talk in other ways. He admits he has Zoe and, unless he hands over his machine, she will be hurt. The Doctor and Jamie are led away.

As they are led towards the lifts, the Doctor tells Jamie he is scared of lifts and can't even press the buttons. Jamie latches on and enters first. The Doctor wheels around to say that he is ready to hand over his machine already. As he does he distracts Packer, pushes him over and activates the lift. As the lift is in motion he destroys the circuits.

Vaughn berates Packer. Packer reviews a report that the lift is stuck. The Doctor and Jamie find a door in the lift shaft. Packer orders all exits to be covered and the lift to be fixed. The Doctor and Jamie have made it to the roof of the lift. They begin to climb the ladder on the side of the shaft.

Packer has the lift working and orders it to be brought back up. As the Doctor and Jamie climb, they hear the lift approaching. As the lift arrives Packer and Vaughn find it empty. Vaughn points out that the lift terminates on the roof. Packer sends some men but then also rides to the top to kill them.

The lift starts again, but the Doctor and Jamie have reached the roof. They find a fire escape and climb down. Vaughn is furious about Packer letting them escape and orders their immediate return.

The Doctor and Jamie find their way through the train carriages, hiding underneath when they hear approaching guards. They decide to hide in a sleeper. Jamie wonders if it is the train that contained Zoe and Isobel. They hear Packer outside and hide in the containers. As Jamie is lying in his, he realises that something is alive in his.

Episode four
The Doctor evades the guards. He frees Jamie from the crate. Jamie says that something was moving inside. They go to investigate, but they are disturbed by an approaching guard and have to flee.

Vaughan berates Packer for losing the Doctor and Jamie. Vaughn explains he intends to stand up to their allies. He explains that Watkins' Cerebration Mentor emits emotion pulses that their allies find distressing. Packer is unsure. Vaughn warns him that their allies are to render everyone non human; instead he wants to use their force and then discard them. Until then Zoe and Isobel are to be hidden away.

Out of sight, the Doctor and Jamie look on as crates are unloaded. Zoe and Isobel are unceremoniously hauled onto their feet. The girls are escorted into the building by several guards. The Doctor overhears that they are being taken to the tenth floor of the central block. Whilst this happens, Jimmy's helicopter flies overhead.

Jimmy reports no sighting of the Doctor or Jamie to the Brigadier. The Brigadier orders Jimmy to withdraw but orders all units to standby.

Packer reports UNIT activity to Vaughn and suspects the Doctor's involvement. Vaughan tells him to leave it with him.

On the roof, the Doctor and Jamie ascend to the next level, where they will try to reach the window where Zoe and Isobel are being kept. Vaughn uses the tannoy to say that unless the Doctor and Jamie hand themselves in in the next ten minutes, Zoe will pay the consequences. The Doctor believes this is enough time for a simple rescue operation.

Isobel is trying to break through the door of the room they are being kept in. Zoe blames herself for endangering her new friend. Zoe and Isobel see the Doctor and Jamie out the window. The Doctor waves to the girls to back away from the window. Zoe looks around the room and spots an electronic eye. She mutters to Isobel that they are being watched. The Doctor asks the Brigadier for help. He asks if the helicopter has a rope ladder and gives him their exact location.

Packer assures Vaughn he has the place covered. Vaughn gives the Doctor his five minute warning. Jimmy's helicopter is heard. Vaughn orders it to be shot down.

The helicopter drops the ladder to Jamie and the Doctor. They lower the rope ladder over the side of the building. Reluctantly, Jamie begins to descend the rope ladder.

Seeing Jamie, Zoe and Isobel barricade the door. Zoe opens the window and Jamie carefully climbs through. Jamie helps Zoe through the window and up the rope ladder.

Below the guards begin to fire. Jamie follows the girls up the rope ladder to the roof. Zoe, the Doctor and Jamie follow Isobel up the rope ladder. Jamie is left on the rope ladder as Jimmy is forced to escape. He clambers on as they are in motion.

Jimmy reports to the Brigadier that all is well. The Brigadier orders all troops to return to base.

Packer fears consequences from their allies. Vaughn shouts at Packer for his subservience to their allies. He orders Watkins' machine to London as he is bringing the invasion forward; it will begin in twenty four hours. Vaughn is to deal with UNIT. Packer leaves. Vaughn rings Major General Rutledge at the Ministry of Defence.

The video phone starts flashing in Rutledge's office. He scrambles the phone line so it can't be traced. Vaughan orders Rutledge to stop UNIT's investigation into IE.

The Brigadier tells the Doctor and his colleagues that they were lucky to survive. The Brigadier is now to take severe action against Vaughn and IE for attempting to shoot down his helicopter. The Doctor starts to hypothesise about what is going on. He remembers the ship on the dark side of the Moon and links it to the deep space transmitter in the IE building. Overhearing this, the Brigadier suggests this could be linked to UFO sightings and goes off to fetch some photographs.

Watkins demands to know what the shooting he heard was and demands to see Isobel. Vaughn dismisses this and tells him his only priority is finishing his machine in the next twenty four hours.

The Doctor studies the photos. They were sighted over the last year, and they all disappeared over South East England, over the IE campus. The Doctor begins to link this to the crates that they discovered. The Doctor decides to go back to the IE building to view the crates, but Jamie is concerned about being spotted. He asks for a map and immediately asks the Brigadier if he has a canoe.

Later the Doctor and Jamie approach the IE building via canal. They breach the building. In the warehouse, workmen are moving the crates around. The workers effortlessly carry the caskets to another area. Slowly, the Doctor and Jamie slink in close enough to watch. The workmen remove the gauze and stand the cocoon up. They attach electrodes to the cocoon. The Doctor confides to Jamie that his fears have been confirmed. The workers turn on the machine. The cocoon begins to writhe until a Cyberman emerges...

Episode five
After seeing the Cybermen reanimated, the Doctor and Jamie decide to return to the canoe and escape.

Back at UNIT HQ, Jimmy and Isobel flirt until they are interrupted by the return of the Doctor and Jamie. Jamie explains to Zoe that they saw Cybermen, whilst the Doctor tries to explain what Cybermen are to Jimmy and Isobel. The Doctor suspects that the deep space transmitters were for the Cybermen to latch onto to find Earth. The Doctor speculates that those people who were acting differently after entering the IE Building must be under the Cybermen's control. The Doctor asks who is in charge of UNIT in England. Jimmy tells him it is Major General Rutlidge.

The Brigadier is in a meeting with Rutlidge and is flabbergasted when Rutlidge tells him to stand down from the IE investigation. The Brigadier implores action, but Rutlidge thinks there must be a misunderstanding and orders him to stop the investigation. Whilst he is talking, Rutlidge seems to lose the ability to speak. The Brigadier begins to suspect foul play and says he intends to send his report to UNIT command in Geneva. As soon as the Brigadier leaves, Rutlidge contacts Vaughn and tells him of the situation — again struggling to talk. Vaughn orders Rutlidge to come to the IE building. When the conversation is terminated, Vaughn tells Packer that he suspects that the control they have over Rutlidge is weakening.

Jimmy informs the Doctor that the Brigadier has already seen Rutlidge. The Doctor worries that their information may now be public.

Rutlidge, now at the IE Building, tells Vaughan they have a maximum of two days before the Brigadier's report will bring further UNIT scrutiny on IE. Packer is concerned by this. Vaughn orders Watkins' Cerebration Machine into the warehouse. Vaughn lifts the wall and communicates with his allies again. He tells them that they will alter the plan and bring the invasion forward. The controller states that the invasion forces are not completed though. Vaughn states that, unless the invasion is brought forward to dawn the next day, he will sever all help. The controller relents.

Down in the warehouse, the workmen are animating more Cybermen. Packer orders them into the sewer and to their different assembly points.

At UNIT HQ, the Doctor is showing the Brigadier the sewer system that stems out from the IE building. Isobel is sceptical about the whole thing, and Jimmy says that even UNIT command will need proof. The Doctor is puzzled over how they are going to form their attack when all of a sudden he remembers the superfluous circuit in Jamie's radio. He asks if there is any more IE equipment in the base. Jimmy leads him off to some.

Gregory and Vaughn are preparing to test the Cerebration Machine on a Cyberman. Gregory is reluctant, but Vaughan forces him. They partially animate a Cyberman before attaching the machine to him and induce fear and transmit it into the Cyberman. The Cyberman rips off the machine and begins to attack all around him. The humans flee, and the Cyberman makes his way into the sewer. Vaughn considers this a success and asks Gregory to up the power on the machine.

Back at base, Isobel has come up with the perfect proof for UNIT command: infrared photography. The Brigadier thinks this a great idea and goes to get some of his men on it. Isobel says she will do it, but the Brigadier says it is no job for a girl. Isobel loses her temper at this sexist attitude, but the Brigadier holds firm. Jamie agrees with the Brigadier. Cross, Zoe and Isobel head off to London to prove the men wrong. Jamie comes with them.

Elsewhere in the base, the Doctor has found the superfluous circuit in an IE computer.

The controller is informing Vaughn of the plan for the invasion. Cyber transmitter units are to be launched an hour before the invasion. They will penetrate through all areas of Earth. They will identify people to be converted into Cybermen whilst the others will be destroyed. Vaughn disagrees with this and says it is counter to their agreement: that Vaughn would be in charge of Earth whilst the Cybermen would be given minerals that they need. The controller demands that if Vaughn is to be in charge he is to be converted. Again Vaughn disagrees; he will have a cybernetic body but not a cybernetic brain. The controller relents. Once the communication is terminated, Vaughan states he doesn't trust the Cybermen and that the audio rejection capsules he has invented will stop them reneging on their deal.

Back at UNIT HQ, the Doctor has decided that in order to properly understand the circuits he needs to go to Watkins' lab at Travers' house back in London. The Brigadier is sending the photography equipment to London by helicopter when the Doctor enquirers as to the whereabouts of his friends. Jimmy tells them they went to London. The Brigadier is fearful they will have gone into the sewers.

In London, Jamie wants to contact the Doctor, but Isobel and Zoe hurry him away. The Brigadier radios Benton and orders him to find the Doctor's friends. He then sends Jimmy to London to search for them.

Jamie, Zoe and Isobel enter the sewers through a manhole but are spotted by a policeman as they do so. Jamie, Zoe and Isobel start to explore the sewers, and it is not long before they spot some Cybermen.

Unbeknownst to them the policeman has climbed down to find them. Isobel is taking photographs of the Cybermen until they are forced to run.

The policeman turns into an oncoming pair of Cybermen and is immediately killed. Jamie, Zoe and Isobel come over his body and realise that they are surrounded from both sides by Cybermen, one of whom is the mad one on whom Vaughan experimented.

Episode six
Two UNIT soldiers, Perkins and Walters, led by Jimmy, meet up with Benton and go into the sewers. The mad Cyberman that has been bearing down on Isobel, Jamie and Zoe walks straight past them. The UNIT forces hear the noise of the mad Cyberman, and Jimmy begins to call out for Isobel, Jamie and Zoe. Isobel wants to meet up with the UNIT forces, but Jamie reminds her that there are Cybermen between them and the soldiers.

The UNIT forces' shouting has drawn the Cybermen's attention. The Cybermen order the forces to obey and to come with them. The UNIT forces prepare a grenade and, when the mad Cyberman distracts the Cybermen, they use the decoy to throw it. It knocks two of the Cybermen out. As the last remaining Cyberman approaches, Perkins loses his courage and runs. He is immediately killed by the Cyberman. The forces make their way back to the ladder and call for Jamie, Isobel and Zoe to meet them there. They all begin to climb the ladder. Jimmy asks Jamie to keep an eye out for the last remaining Cyberman.

As they approach the surface, Jamie's leg is caught by the Cyberman. Walters comes and drives the Cyberman back down into the sewers with his rifle butt. Benton then arrives and drops a grenade into the sewers, destroying the last Cyberman.

The Doctor is still poring over the circuits and is still utterly bamboozled. The Brigadier tells him he is soon heading to Geneva and that after that there might be two or three days before action. The Doctor is perturbed — it may be too late by then. Isobel enters with the photos she took of the Cybermen. The Brigadier is a little disappointed as they look fake. Isobel is annoyed at this.

Packer reports the UNIT attack of the Cybermen to Vaughn. Vaughn is not worried and states that the invasion will be too soon for UNIT to do anything. Watkins and Gregory come up with the modified Cerebration Machine. Watkins is now very aware his machine has been turned into a weapon. Vaughn uses the machine on Watkins, knocking him down. Gregory stands up for Watkins, and Vaughn threatens him with the same treatment. Vaughn orders the machine into mass production. A weakened Watkins vows that if he ever gets the chance he will kill Vaughn. Vaughn calmly asks for Packer's gun. He points it at Watkins' head before handing him the gun and ordering him to shoot. Watkins hesitates. Vaughn slaps him and calls him a coward. Watkins shoots. The bullets, despite clearly entering Vaughn's chest, have no effect on him. Vaughn laughs as Watkins faints with shock.

The Doctor and Jimmy are still experimenting on the circuits. Isobel and Jimmy flirt some more until they are interrupted by a report from the UNIT forces in London. They report that Watkins is being escorted away from the IE building. The Brigadier toys with a rescue mission. Isobel pleads with him whilst the Doctor states he would be very useful. The Brigadier agrees. Jimmy is to lead a full assault platoon on the mission.

Later Gregory recounts how thirty UNIT forces killed the two guards and took Watkins. Gregory only survived as he ran away. Vaughn orders the Cybermen to kill him. In the sewers, Gregory is killed by the Cybermen.

Watkins, now back at his lab, says he has no idea about the circuits, but his account of what Vaughn has done to his Cerebration Machine causes the Doctor to realise. The circuits are emotional circuits used in a similar way to Watkins' machine. He runs to the lab to experiment. The Brigadier tells Jimmy he is heading off to Geneva.

Soon enough, the Doctor has figured out the Cybermen's plans. They intend on using their ship, parked on the dark side of the moon, to boost the signals from their satellites, magnify them and beam them back down to Earth. When they come into contact with the monolithic circuits in the IE equipment, they will produce cyber-hypnotic signals and render humans under Cyberman control. The Doctor reminds Zoe of the depolarisers they used back on the Wheel when they first met. Zoe and Watkins set about making some.

In Vaughn's office the alarm goes off, and Vaughn raises the wall to commune with the Controller. There is one hour until the invasion and transmission of the cyber-signal is to start.

The Doctor informs the Brigadier of the new developments. The Brigadier vows to inform UNIT headquarters and begin making depolarisers. Zoe and Watkins, however, have only found enough equipment for three. The rest go on a mad search for more equipment.

The Controller tells Vaughn that all will be ready in thirty minutes. When the wall is down, Vaughn tells Packer that he is half an hour away from controlling the world. Packer is sceptical.

Jimmy and Isobel talk. Jimmy is beginning to think the Doctor may be wrong when they begin to hear an electronic high pitched noise. The Doctor falls to the ground. His depolariser has fallen off. The depolariser is placed back on but to, seemingly, no effect.

In a similar way people all over London are brought to their knees by the sound ringing in their ears. Simultaneously hundreds of Cybermen have emerged from the sewers and are walking the streets of London.

Episode seven
The Doctor wakes up from his attack. Jimmy radios to check the Brigadier — he is fine but half of UNIT's forces have been rendered unconscious. The Brigadier arranges for the Doctor and the rest of the forces to come to Geneva.

The Controller informs Vaughn that the invasion forces are being prepared. Vaughn says his radio beams are ready to guide them in. Vaughn now tries to gain power over the Cybermen. He says he will remove all support unless he has full control, over all the Cybermen. The Controller agrees. Vaughan terminates the conversation. Once the wall is down Vaughn radios Packer and tells him that now the UNIT forces are neutralised he can go and get Watkins back to allow the Cerebration Machine to be put into production.

The UNIT transportation arrives at Watkins' lab. No sooner have they got in the door than Packer and his men arrive. Jimmy hurries everyone out of the back door. A gun breaks through the glass in the front door and shoots. Jamie and Watkins are hit.

The Brigadier receives a transmission from Jimmy asking for a helicopter. The Brigadier arranges it.

Back at the IE Building, Vaughn does not understand how the UNIT forces are still active. Packer blames the Doctor. Vaughn says the invasion will still continue. Packer asks how they will resist the Cybermen without Watkins' machine. Vaughn remains confident, but Packer remains sceptical.

The Doctor's party have joined the Brigadier and the forces on the UNIT plane. The Brigadier is informed that UNIT HQs are unresponsive in New York, Moscow and Peking. Jimmy wonders if they would be able to make enough depolarisers for everyone; the Doctor states that they have too little time. The only way that they can take the main cyber ship down is with a huge missile; however, the Brigadier says that only Russia and America have such weaponry. He does have an idea though. Going to a safe, he uncovers a document that informs UNIT that the Russians were going to send a rocket into space on the day of the invasion. If they were to switch the astronaut's capsule with a warhead, they could render the rocket into a missile. Jimmy is sent away to deal with it. The Brigadier also asks if anti-missile missiles could be used to take down the small invasion ships. The Doctor suggests that would work, and the Brigadier goes off to organise it. Zoe informs the Doctor that the injury Jamie sustained was just a flesh wound and that he will be fine. The Doctor tells Zoe she is to stay with the Brigadier and help him using her computing skills. The Doctor informs her and the Brigadier that he is going to seek an audience with Vaughan. The Brigadier blocks this, but the Doctor states that it is the only way they will gain more information. He will use the transmitter given to him to relay all the information back to UNIT. When asked about how he will access the building without getting caught by Cybermen, the Doctor states that the answer is simple: through the sewers. The UNIT plane prepares for landing.

As soon as the plane lands the Doctor and Jimmy head off in different directions. The plane takes off again, heading towards the military base. The Brigadier sends a helicopter to the IE building in case the Doctor needs assistance.

Later, the Doctor radios the Brigadier and tells him he is in the sewer system. He flips a coin to decide which way to go and heads off. Zoe is worried about the Doctor but the Brigadier placates her. He is informed that Jimmy is on board a plane to Moscow.

Packer is in Vaughn's office, showing him the positions of the Cybermen forces on a map. He is concerned they are not at full capacity, but Vaughn calms him saying they will soon arrive. A security alarm goes off. Vaughn turns to the cameras and soon finds the Doctor talking directly into the camera. He says he will pop up for a chat with Vaughn. Packer is ordered to stand by. Packer wants to kill the Doctor, but Vaughn wants to use him as insurance.

The Doctor radios the Brigadier to say he is "entering the lion's den". The Brigadier orders that the conversation be recorded and that if the Doctor is in danger all available force should be used to extricate him.

The Doctor questions Vaughn on why he is helping the Cybermen. Vaughn reveals he has been working with the Cybermen for five years. Vaughn contacted them and helped guide them to Earth. The Doctor tries to convince Vaughn that he is just being used as a pawn. The Doctor makes Vaughn squirm when he points out that, without Watkins' knowledge of his machine, Vaughn is at the mercy of the Cybermen.

The Brigadier arrives at the military base to find all the men unconscious. Zoe and the UNIT forces go about equipping them with depolarisers. The Brigadier receives news that Jimmy is over the Russian borders. There is no new news from the Doctor.

Vaughn believes that the Doctor has been merely sent to divert him and waste his time while UNIT prepare something. He calls Packer and orders him to turn in the beam to summon the invasion fleet.

The major at the military base, Branwell, is sceptical of the story the Brigadier tells him. There is nothing on the radar, but Zoe says this is because the Cyber Fleet are out of range. Branwell decides to arm the missiles in readiness.

The Controller tells Vaughn that the transporters are ready to launch in two waves. The Doctor pleads with Vaughn to stop the invasion.

The message that the invasion is beginning has been relayed to the Brigadier. He is also told that Jimmy has landed in Moscow. The transporters have started showing up on the radar and are mere minutes away. Branwell wants to use some of his missiles to take out just the leading transporters. Zoe reckons that if they use all their missiles they can destroy 90% of the fleet using a chain reaction effect. The Major pooh poohs this, saying that the calculations would prove too lengthy. Zoe says she can do it in thirty seconds. The Brigadier implores the major to allow her to try. After thirty seconds of frenetic activity, Zoe has produced the calculations, which are fed into the machine. Branwell allows the launch.

In space the missiles start to crash into the transporters.

The Controller reports this attack to Vaughn and says that they have been betrayed by him. Vaughn strenuously denies this. The Controller states that the Cybermen are now going to take full control. Vaughn tries to disagree and approaches the Controller. The machine stuns him. The Controller explains that a cyber megatron bomb is being delivered which is to wipe all living beings off the face of the Earth. The Doctor asks a semi-conscious Vaughn if this is the world he wanted to rule.

Episode eight
Isobel listens in to the conversation between the Controller, Vaughn and the Doctor. When they hear news of the bomb, UNIT contact the Brigadier.

The Brigadier, Branwell, Zoe and the troops are celebrating the destruction of the Cyber Fleet when the call regarding the bomb comes through. The Brigadier sets off for his plane, ordering Branwell to keep his eyes on the radar for signs of the bomb.

Vaughn argues with the Controller to no avail and, in panic, uses the Cerebration Machine. The Controller starts to malfunction as the Doctor begs Vaughn to stop, worried the machine will blow the IE building sky high. The machine explodes, knocking the Doctor and Vaughn backwards. Vaughn is happy, but the Doctor points out there are hundreds of Cybermen in the streets and hundreds more about to land. The only way to stop them delivering the bomb is to knock out the radio beam which guides them to Earth. Vaughn radios for Packer but instead is met with the face of a Cyberman. Packer appears, panicked. The building is being swarmed by Cybermen. A Cyberman enters and kills Packer. The Doctor uses the Cerebration Machine on it. Vaughn tells the Doctor that the transmitter is at the IE Compound. The Doctor radios the Brigadier and presents him with two options: they either cut off the transmitter or destroy the cyber ship. The Brigadier tells the Doctor that the Russian rocket is still ten hours away so they will have to go for the transmitter. The Doctor pleads with Vaughn for his help. Vaughn is reluctant and despondent; he still believes he should rule the world but will help the Doctor as he hates the Cybermen. The Brigadier sends a helicopter, and the Doctor and Vaughn make their way to the roof, taking the Cerebration Machine for back up.

The Brigadier rues the fact he only has one platoon to help the Doctor. Jimmy radios and tells the Brigadier the rocket has been armed with the warhead. The UNIT plane takes off.

Branwell is sceptical the plan will work.

The Russian rocket launches.

The Doctor, now safely in the helicopter, radios the Brigadier to say they are nearing the compound. The Brigadier tells the Doctor to wait for him and his UNIT forces, but the Doctor says there is no time and they have the Cerebration Machine to protect them. The Brigadier tells the helicopter to hover over the Doctor at all times so that when UNIT arrive they will be able to locate him. Isobel and Zoe ask the Brigadier if they can accompany them when they land. The Brigadier reluctantly agrees.

Now in the compound, Vaughn wants to go in all guns blazing, but the Doctor suggests they should be more covert. They do not get very far before they are forced to kill a Cyberman and blow their cover. They decide to go over the roofs to avoid detection. The transmitter is within their sight, but it is surrounded by Cybermen.

UNIT arrive and make their way towards the Doctor.

The Doctor and Vaughn make their way towards the transmitter pursued by four Cybermen. They climb down a ladder onto ground level to evade them.

The UNIT forces encounter a dozen Cybermen and engage them in battle. There are casualties on both sides. The battle ends when the Brigadier orders the UNIT forces to wipe out the Cybermen with a bazooka. All the time Isobel is photographing events.

The Doctor and Vaughn have made their way to the entrance to the transmitter, but there are no Cybermen to be seen. Vaughn makes his way up the steps, but it is an ambush. Vaughn uses the Cerebration Machine to kill two Cybermen, but he is killed by the third. The third Cyberman fires at the Doctor three times, but the Doctor evades the blasts. He encounters the Brigadier, who orders the Doctor to duck and uses the bazooka to nullify the Cyberman before going on to the transmitter building. Isobel stops to take a picture of the Doctor.

The Brigadier reports to all UNIT forces that the bomb can no longer be delivered, but half the world is still unconscious. They need to destroy the cyber ship, but the Russian rocket is still six hours away.

Branwell detects the cyber ship on his radar. It is visible but out of range.

The Brigadier is stumped as to why the cyber ship would be getting closer. He wonders if it is to avoid the Russian rocket, but the Doctor suggests it is to deliver the bomb in a different way. The Brigadier asks if Jimmy can turn the missile. He says he can and that impact is in twelve and a half minutes. The Doctor suggests that may be too late.

Time passes slowly as they wait for the bomb or the rocket.

Branwell sees the rocket approaching the ship, but also sees the bomb being dropped. He raises the missiles. The bomb is thirty seconds from landing. He launches the missiles. They miss. He launches a second set. It hits destroying the bomb. At the same time, the Russian rocket hits and destroys the cyber ship.

Later Zoe is modelling again for Isobel. It is her last photo shoot as she has got a job working for a publishing company off the back of her photos of the UNIT and Cybermen battles. The Doctor is finishing his circuits to repair the TARDIS, whilst Jamie is having a check up at the hospital. Jimmy, who is now together with Isobel, says that the Doctor is ready and that they can pick Jamie up and take them all wherever they need to go.

Jimmy and Isobel drop the Doctor, Jamie and Zoe off in the middle of a field, much to their bemusement. There is no sign of the TARDIS. The Doctor gropes about for it before he leans against its invisible form. He enters and renders it visible. Zoe and Jamie enter and the machine dematerialises, much to the bewilderment of Jimmy and Isobel.

Cast

 * Dr. Who - Patrick Troughton
 * Jamie McCrimmon - Frazer Hines
 * Zoe Heriot - Wendy Padbury
 * Isobel - Sally Faulkner
 * Tobias Vaughn - Kevin Stoney
 * Packer - Peter Halliday
 * Lorry Driver - Murray Evans
 * Benton - John Levene
 * Tracy - Geoffrey Cheshire
 * Patrolman - Walter Randall
 * Gregory - Ian Fairbairn
 * Brigadier Lethbridge-Stewart - Nicholas Courtney
 * Sergeant Walters - James Thornhill
 * Captain Turner - Robert Sidaway
 * Professor Watkins - Edward Burnham
 * Phone Operator - Sheila Dunn
 * Major-General Rutlidge - Edward Dentith
 * Cybermen - Pat Gorman, Charles Finch, Derek Chaffer, John Spradbury, Terence Denville, Ralph Carrigan (misspelt Ralph Carrigon), Richard King, Peter Thornton
 * Workman - Peter Thompson
 * Policeman - Dominic Allan
 * Private Perkins - Stacy Davies
 * Major Branwell - Clifford Earl
 * Sergeant Peters - Norman Hartley

Uncredited cast

 * IE Patrolmen - Peter Pocock, Ray Ford
 * IE Guards - Dave Carter, Terry Duggan, Leslie Bates, Brian Nolan, Maurice Brooks, Kenneth Hale, Alistair McFarlane, Ron Conrad, Derek Slater
 * Cyber Director/Cybermen Voices - Peter Halliday
 * UNIT Soldiers - Charles Finch, Roy Pearce, Ross Huntley, Steve Kelly, Leslie Conrad, James Holbrook, Richard Kitteridge, Gary Dean, Barrie Dupres, Maurice Brooks, Billy Horrigan, Alan Chuntz, Terry Walsh
 * Warehousemen - Gordon Stothard, Miles Northover, John Lord
 * Londoners - Trevor Shewring, Simon Stapely, Roy Denton, Lyn Denton
 * Henlow Downs Bunker Men - Tony Manning, Mike Lee, David Pelton, Derek Slater
 * Extras - Charles Finch, Clark Reed, Victor Munt, Crawford Lyle, Peter Roy, John Kielty, Ron Ringer, Harry Martin, Robert Pearce, Bobby Beaumont, Reg Cranfield (all DWM 189)

Crew

 * Assistant Floor Manager - Sue Willis
 * Costumes - Bobi Bartlett
 * Designer - Richard Hunt
 * Film Cameraman - Alan Jonas
 * Film Editor - Martyn Day
 * Film Sound Recordist - Bill Chesneau
 * Incidental Music - Don Harper
 * Make-Up - Sylvia James
 * Producer - Peter Bryant
 * Production Assistant - Chris D'Oyly John
 * Script Editor - Terrance Dicks
 * Special Sounds - Brian Hodgson
 * Studio Lighting - Robbie Robinson
 * Studio Sound - Alan Edmonds, Bryan Forgham
 * Theme Arrangement - Delia Derbyshire
 * Title Music - Ron Grainer
 * Visual Effects - Bill King, Trading Post

Cultural references from the real world

 * "Kilroy Was Here" can be seen written in the lift shaft.
 * Isobel plays "Teddy Bears' Picnic" on her gramophone.

Species

 * Jamie mentions the Yeti to the Brigadier.

Devices

 * ALGOL is a language understood by computers.
 * The visual stabiliser circuit controls the TARDIS' outward appearance; removing it renders it invisible.

The Doctor

 * The Doctor drives a UNIT jeep.

The Doctor's items

 * The Doctor uses his recorder as a telescope.

Individuals

 * Gordon Jones is a lecturer at Churchill College, Cambridge.

Astronomical objects

 * The Cybermen have a spaceship hidden behind the far side of the Moon.

Production

 * This story had a working title of Return of the Cybermen, which was later changed to The Invasion to keep the Cybermen's reappearance a surprise until episode four. It was originally conceived as a four-part story and got expanded to eight when the next story, The Dreamspinner, fell through.
 * Only episodes two, three, five, six, seven and eight of this eight-part story exist in the BBC Archives as 16mm black & white film telerecordings.
 * This story marked the debut of Terrance Dicks as script editor and his first credited contribution to the series. Dicks went on to write or co-write a number of episodes and become best known for his work of writing novelisations for Target Books and eventually contributing to most lines of original fiction based upon the series on into 2008.
 * Together with The Web of Fear, this story was a sort of "test run" for a format switch. For the next two or three seasons, most stories would feature the Doctor working with UNIT to protect humanity on more-or-less modern-day Earth.
 * Dialogue places this story four years after the events of The Web of Fear. This story is also placed "some months" before Spearhead from Space, according to dialogue in that story.
 * While the Cybermen would continue to change their appearance on the series, as they had done since their introduction, this story set the basic design for them, first developed for this story by Bobi Bartlett, through the 1980s. Cybermen emerging from cocoons was also used in Earthshock. They also operate in the London sewers in Attack of the Cybermen. A mass invasion of London by Cybermen also features in the Series 2 stories, Rise of the Cybermen, The Age of Steel, Army of Ghosts and Doomsday, the Series 8 stories, Dark Water and Death in Heaven, and in the Doctor Who Magazine comic The Flood.
 * Cybermats were to have appeared in this story.
 * It was during filming of this story that Frazer Hines announced his intention to leave the series.
 * Zoe makes no appearance in episode three of the story as Wendy Padbury was on holiday during the week when it was recorded. Similarly, Jamie appears only in a pre-filmed insert in episode eight as Frazer Hines was due for a break.
 * A black and white shot of a Cyberman, with two others behind, walking down the steps of St. Peter's Hill, with St. Paul's Cathedral in the background, accompanied the Radio Times programme listing for episode one, bearing the title Invasion and with the accompanying caption, "Dr. Who starts a new adventure today at 5.15 — one that will bring him face to face with some of his deadliest enemies, the Cybermen".
 * The following piece of behind-the-scenes information appeared at the foot of the Radio Times programme listing for episode five: "For this Dr. Who story more filming was done on location than ever before, and the production team were fortunate to have the co-operation of both the Army and Air Force on scenes that involved such equipment as jeeps, a transporter plane, a three-ton lorry, and a rescue helicopter."
 * Nicholas Courtney reprises his role as Lethbridge-Stewart, now promoted from Colonel to Brigadier, from The Web of Fear.
 * John Levene (Benton) previously appeared as a Cyberman in The Moonbase and as a Yeti in The Web of Fear. He was initially contracted to play a Cyberman in The Invasion but landed the role of Benton after the actor originally cast – who shall remain nameless – was fired by Douglas Camfield for continually turning up late for filming, causing the planned shooting schedules to be changed.
 * John Levene (Benton) was uncredited on-screen for episode five but was credited in Radio Times.
 * Peter Halliday also provided, uncredited, the voices of the Cybermen in episodes six to eight and of the Cyber Director — hidden in a concealed compartment in Vaughn's office — in episodes two and five to eight.
 * Norman Hartley (Sergeant Peters) was credited as "Sergeant" in Radio Times for episode eight.
 * The actors playing the Cybermen were credited on-screen, but not in Radio Times.
 * In the DVD's animated version of episode one, the words "Bad Wolf" (the story arc of the 2005 series) are written on Isobel's wall as an in-joke.
 * Also in the animated episode one, the car that the Doctor, Jamie and Zoe hitch a ride with after the lorry driver is shot has the licence plate H 23 63, which is a reference to the date of the original broadcast of An Unearthly Child, the very first episode of Doctor Who, on 23 November 1963.
 * Additionally, the animators got Zoe's costume wrong; for the beginning part of the missing episode one, Zoe would have worn her catsuit from The Mind Robber and she would have changed when Isobel got her fixed up with "some proper gear".
 * The episode was intended to prove that Earth-based stories could be produced cheaply and effectively. Ironically, it was the most expensive Doctor Who episode ever produced when made, and remained so for several years.
 * Originally, Professor Travers and his daughter Anne were to appear, but they were replaced by Isobel and her uncle when Mervyn Haisman and Henry Lincoln refused to grant the rights. The DVD's production subtitles claim they were granted rights to the characters, but as the characters became less involved in the story, they thought it was not worth including them. The characters are mentioned in dialogue, however: Isobel lives in Travers' former house in London, and Professor Watkins mentions that Travers was getting "past it", so he persuaded him to live in America with Anne.
 * The prologue of the novel Iceberg opens during the Cybermen invasion in this story. The Cybermen in that novel are said to be from Planet 14, which was first mentioned in The Invasion by the Cyber-Planner. The comic story The World Shapers also picks up on the Planet 14 reference, though it explains it away in a very different way. Since The Invasion takes place in either in the late 1960s or 1970s (see UNIT dating controversy) and no other televised Cybermen story had taken place prior to 1986 (the date of The Tenth Planet), the Doctor must have met the Cybermen before in an untelevised story.
 * A reference to Planet 14 is once again made in the 2017 finale The Doctor Falls.
 * This story's writer, Derrick Sherwin, would later produce the series, making him the only producer in the Classic Series to also be credited as a writer, though others would write for the series under pseudonyms.

Influences

 * The influence of the various spy thriller films and television shows which were popular at this time are very clear. Tobias Vaughn is similar to the supervillains featured in the James Bond films and The Avengers. The Doctor acting as advisor to a military group dealing with an otherworldly menace is highly reminiscent of the Quatermass serials. Specifically, the plot of The Invasion has some similarity to, though not as much as some other Doctor Who stories, such as Spearhead from Space.

Ratings

 * Episode one - 7.3 million viewers
 * Episode two - 7.1 million viewers
 * Episode three - 7.1 million viewers
 * Episode four - 6.4 million viewers
 * Episode five - 6.7 million viewers
 * Episode six - 6.5 million viewers
 * Episode seven - 7.2 million viewers
 * Episode eight - 7.0 million viewers

Filming locations

 * The cow pasture in which the TARDIS materialises was located at Williamstrip Farm at Coln St Aldwyns. Professor Watkins' house was located at St James' Gardens in Kensington.
 * Kingston Minerals in Kempsford served as the IE compound, while the compound's roof was actually that of the Associated British Malsters' Guinness factory in Wallingford, Oxfordshire.
 * Additional scenes at IE were filmed at the Guinness Factory in London.
 * The canoe sequence was filmed at Lisson Grove and the helicopter sequence at Denham Aerodrome in Buckinghamshire.
 * Other scenes were filmed at various locations in Gloucestershire.
 * Ealing Television Film Studios, Ealing Green, Ealing
 * Lime Grove Studios (Studio D), Lime Grove, London

Production errors

 * In episode two, Wendy Padbury mispronounces "integer" while speaking to the IE computer in ALGOL.
 * In episode five, the panel concealing the Cyber Director struggles to close.
 * The Cyberman falling from the roof of an IE building in episode eight is clearly an empty costume.
 * In episode eight, the strings that make the Cyber Director's "head" twist are clearly visible.
 * In episode four, the Doctor and his companions claim to have seen a ship on the moon — when they didn't. (In the DVD's animated episode one, a ship was added to cover this up.)
 * The Cybermen wear silver painted tennis shoes.
 * In episode eight, Wendy Padbury fluffs her line regarding the distance to the Cyber Ship, quickly correcting "30—" to say "50,000 miles."
 * Throughout, Brigadier Lethbridge-Stewart's moustache changes size and shape.
 * Some episodes of the story were broadcast in such an amplitude that sometimes makes it hard to make out what the cast were saying.

Continuity

 * Tobias Vaughn returns in PROSE: Original Sin, in which it is revealed that not only did he survive by transferring his mind into a cybernetic body, but funded the development of BOSS, Operation Golden Age, and Professor J. P. Kettlewell's robot, and influenced the expansion and policies of the Earth Empire.
 * Isobel's photographs of the Cyberman invasion were later derided as fakes and she became a standing joke on Fleet Street. The journalist James Stevens was highly dubious of her claims that the Earth had been invaded by "robot men from outer space." She was threatened by a man with a lisp and her boyfriend left her as his career was at risk because of their relationship. (PROSE: Who Killed Kennedy) However, her boyfriend was not Jimmy Turner as they later married. (PROSE: The Scales of Injustice)
 * The majority of, if not all of the Cybermen in this story were upgraded from the colonists on Isos 2. (AUDIO: The Isos Network)

DVD releases

 * Released as Doctor Who: The Invasion, the DVD makes use of animated versions of the missing episodes one and four that were made by Cosgrove Hall, which had previously made Scream of the Shalka for the now-defunct BBCi website.

Release dates

 * Region 2 - 6 November 2006
 * Region 4 - 3 January 2007
 * Region 1 - 6 March 2007

Features

 * Commentary on episode one by James Goss (bbc.co.uk), Steve Maher (Cosgrove Hall films) and Mark Ayres (audio cleanup).
 * Commentary on episodes two to eight by Frazer Hines, Wendy Padbury, Nicholas Courtney and Chris D'Oyly John.
 * Flash Frames - A featurette about the creation of the animated episodes one and four, including interviews with the animation team at Cosgrove Hall.
 * Love Off-Air - An affectionate tribute to the people dedicated enough to capture the soundtracks of Doctor Who in the 1960s, enabling the recreated episodes on this DVD.
 * Trailers - Two animated trailers.
 * Character Design - Showcasing Steve Maher's character design drawings and animation tests.
 * Evolution of The Invasion - Cast and crew recall the making of The Invasion, featuring contributions from Padbury, Hines, Courtney and D'Oyly John, plus Kevin Stoney (Vaughn), Sally Faulkner (Isobel), Peter Halliday (Packer), Edward Burnham (Watkins), Ian Fairbairn (Gregory) and Terrance Dicks (Script Editor).
 * VHS Links - Nicholas Courtney's links from the 1993 video release of The Invasion
 * Photo Gallery - Includes music by Don Harper and John Baker as well as special sound by Brian Hodgson.
 * Production Subtitles

The animated episode one on the DVD release makes some changes to the episode, as noted on the commentary:
 * After the TARDIS is attacked, a ship goes across screen (put in by the animators to cover a plot hole).
 * The sequence after the Doctor leaves the van that takes them out the compound is shortened.
 * The words "Bad Wolf" are put on the wall where Isobel Watkins leaves notes, making reference to the Bad Wolf meme.

Notes:
 * Editing for the DVD release was completed by the Doctor Who Restoration Team.

BritBox streaming availability
This story (with animated reconstructions of episodes 1 and 4) is available for streaming through BritBox (US) as part of Season 6 of Classic Doctor Who.

VHS release
This story was released as Doctor Who: The Invasion in 1993 as a double video pack, with an introduction and linking material by Nicholas Courtney to cover the missing episodes one and four.

Release dates

 * UK June 1993
 * PAL - BBC Video BBCV4974


 * US June 1995
 * NTSC - CBS/FOX Video 8251
 * NTSC - Warner Video E1273

Audio releases
This story was released as Doctor Who: The Invasion as part of the BBC Radio Collection. It includes the original soundtrack of the serial with linking narration by Frazer Hines. It also includes a bonus interview with Hines.

It was first released on 1 November 2004 in the Cybermen box set (ISBN 0-563-52508-8), a special 3-CD tin which also contained the soundtrack of The Tenth Planet and a bonus disc. It was subsequently released individually on 9 January 2006 (ISBN 978-0-563-52327-7). It is scheduled to be re-released as part of Doctor Who: The Lost TV Episodes - Collection Five on 2 August 2012 (ISBN 978-1-4084-6755-8).

Unofficial releases
Loose Cannon Productions have made a reconstruction of the missing episodes one and four, using audio recordings, authentic pictures, composite pictures, pictures from other stories and specially created material. (Note: The surviving episodes are not included on the recon.)

Although Loose Cannon Productions and Cosgrove Hall were working from the same scripts and audio recordings, their visual interpretations of the episodes are very different and it is interesting to compare the two.

Features

 * Celebrity Introduction by Kevin Stoney (Tobias Vaughn)
 * Production Featurette
 * An Interview with Kevin Stoney (also includes clips from many of his television and film appearances)
 * A re-enactment of the scene of Cybermen descending the steps of St. Peter's Hill near St Paul's Cathedral, using Earthshock-style Cybermen, and comparing the re-enactment with the original.