Turn Left (TV story)

Turn Left was the eleventh episode of series 4 of Doctor Who.

It was the first Doctor-lite episode to focus on the main companion without the Doctor, and marked the first major reappearance of Rose Tyler. It also showed a parallel world showing what would have happened had Donna not met the Doctor in The Runaway Bride. In that world, without Donna to convince him to leave during his encounter with the Empress of the Racnoss, the Doctor ended up drowning in the resulting flood under the Thames, because of this, many of the Doctor's companions and friends would have died, and without the Doctor around to stop an overwhelming threat on the horizon, all things would eventually be destroyed. Much of series 3 and 4's events set on present-day Earth would still occur but would have cost more lives without the Doctor's intervention. The Master would not have been present in his Harold Saxon persona as the Doctor would not have been alive to go to the year 100 trillion to allow him to escape the end of the universe. Indeed, the year 100 trillion itself would never occur, as the "stars go out" in 2009.

The main villains in this episode were agents of the Trickster's Brigade, a group who feed off altering timelines. They are also the only enemy to have been fought in Doctor Who and its spin-off shows Torchwood and The Sarah Jane Adventures.

Synopsis
On an alien planet, Donna meets a fortune teller, who launches her into a world based on one question: "What would happen if Donna never met the Tenth Doctor?" Without the Doctor, the whole world is in ruin, and a mysterious blonde tries to warn Donna of the oncoming darkness... Now a simple refugee, Donna is the only one who can undo the damage. But how?

Plot


The Tenth Doctor and Donna are in a bustling marketplace on an alien world, mixing with the locals. Donna wanders away from the Doctor to explore as he chats away with a merchant. A mysterious fortune teller asks if she wants her future told, but Donna declines. The fortune teller then says the reading is free for those with red hair. Donna smiles and relents. As the fortune teller asks about Donna's past, she sees there is a man in her life that changed everything. Donna tells the fortune teller that she met the man on Christmas Eve, when she ended up on his spaceship on her wedding day. She was a temp at H.C. Clements on Earth. Donna experiences a flashback, but the fortune teller dismisses it. The teller asks Donna what event led to her meeting with the Doctor and Donna says it was six months before.

At that time, Donna and her mother were in Donna's car at a T-junction, arguing about her future. Sylvia tried to persuade Donna to turn right and ask businessman Jival Chowdry for a job, but Donna turned left to go to her planned temp job at H.C. Clements. After experiencing another flashback, Donna is now panicking, but the fortune teller asks her what would have happened if she turned right as something crawls onto Donna's back. Scared, Donna falls under the fortune teller's influence and, in the past, she gives in to her mother's nagging and turns right, and because of that one fateful decision everything changes....

On Christmas Eve, Donna is at a Christmas party with the rest of the staff from her workplace. She has just been promoted to Jival Chowdry's personal assistant. Suddenly the Racnoss Webstar attacks London, and is destroyed by the army at a terrible cost. During the chaos, Alice stares at Donna's back, looking terrified. When Donna acts astonished that Alice's attention is focused on her despite the ongoing chaos, Alice, terrified, says that there is something on Donna's back. After this, Donna runs to the Webstar's general location. There she finds an ambulance. Near the ambulance and a group of UNIT vehicles, Donna overhears a UNIT officer talking into a radio about "the Doctor" who drowned beneath the Thames. As the Doctor's body is loaded into an ambulance, a hand falls out of the stretcher, dropping a sonic screwdriver. As Donna walks away, Rose Tyler comes running down the street and asks for information about the body that has just been loaded into the ambulance. She is stunned to hear that it was the Doctor, despite Donna's assurances that it could have been any doctor. Rose vanishes moments later.

Donna has been fired from her job. Chowdry tries to tell her that he has to lay people off because half of his contracts are on the other side of the river. Even though it has been several months since the Racnoss attack, the Thames is still closed off. Meanwhile, the Royal Hope Hospital is mysteriously transported to the Moon. When it returns, there is only one survivor: medical student Oliver Morgenstern, who relates the terrible events involving "talking rhinos". Wilfred, Donna's grandfather, believes that the rhinos are aliens. Morgenstern tells reporters he only survived when fellow medical student Martha Jones gave him the last of her oxygen before she died, and that Sarah Jane Smith had taken control of the situation and said she could stop the MRI. Sarah Jane's body was reported as being recovered from the hospital, while it is feared that Sarah Jane's son Luke and Luke's teenage friends Maria Jackson and Clyde Langer had also perished inside.

As Donna digests the terrible news, Rose tells Donna that she should go to the country for Christmas. When Donna says that she can't afford it, Rose mentions the raffle ticket she bought at work; First prize, luxury weekend break. Donna looks confused and leaves.

Donna takes the woman's advice and treats her mum and grandfather to a Christmas holiday in the English countryside. On Christmas morning, the housemaid comes in to bring the Nobles their breakfast but then recoils from Donna and repeatedly shouts "You've got something on your back!" in Spanish. This is quickly forgotten when a newsflash shows that a replica of the Titanic is about to fall on Buckingham Palace. Suddenly the TV signal cuts off just before a tremor from the impact hits the hotel. The three run outside and watch, horrified, as a mushroom cloud rises above London. Sylvia is aghast with shock as she realises that everyone they know is now dead, while Wilf notes that if Donna hadn't won the raffle they'd have been killed too.

With London destroyed and all of southern England has been flooded with radiation, the Nobles are considered refugees and forced to move to Leeds. France has closed its borders. They are allocated a house that is shared with two other families. Although Wilfred puts on a brave face and tries to make the best of things, Sylvia just feels utter hopelessness with her family's new situation.

In 2009, the United States pledges to help Britain with monetary relief but must abandon the plan when their own crisis strikes: sixty million Americans are killed when they are turned into Adipose.

Sometime later, Donna finds soldiers firing at cars when the Sontarans activate the ATMOS devices, covering the Earth with a poisonous fog (although the UK isn't too badly effected as there is now barely any petrol in the country). A soldier notices something on Donna's back and holds her at gunpoint, but she is released when it is revealed that nothing is there. That night, Donna meets Rose for the third time. Rose explains that the Torchwood team, aboard the Sontaran ship, are trying to stop the catastrophe. Suddenly, the sky is cleared by an atmospheric converter. Gwen Cooper and Ianto Jones have given their lives to achieve this, and Captain Jack Harkness has been transported to the Sontaran homeworld.

Rose refuses to tell Donna her name. She only says that she has "crossed reality", and tries to explain that Donna had saved the Doctor's life in an alternate timeline, though Donna insists that she had never met him. Rose warns Donna that the coming "darkness" threatens every single universe, assuring her she is the most important woman who has ever existed. Donna tries to walk away, but Rose tells her that she will decide to go with her in about three weeks and makes a cryptic remark about Wilf's telescope. She warns Donna that when she comes with her, Donna will die. Then she disappears.

Three weeks later, the genial Italian family in Donna's house is evicted as England is now "only for the English". Since the oceans are closed off, they must be taken to a "labour camp". "That's what they called them ," Wilfred says horrified, "it's happening again!" Later at night, Donna and Wilf talk about recent events while looking through his telescope. He notices that the constellation of Orion has gone, though there are no clouds. Suddenly other stars start to disappear from the sky as if they were never there. Donna finds Rose and tells her that she is ready.

Rose takes Donna to a UNIT base and shows her the TARDIS — salvaged from beneath the River Thames — which is dying after the Doctor's death. Rose asks Donna if she wants to see the creature on her back. They step into a circle of mirrors and lights, with pieces of technology which seem to be scavenged from the TARDIS. Rose switches on a light which reveals what is on Donna's back: a "Time Beetle". Donna is horrified and begs Rose to get it off her. However, Rose explains that it "feeds off time by changing time" and that she thinks the beetle is in a state of flux, although when Donna asks what that means, Rose says she doesn't know, but that it's something the Doctor would say. She also says the beetle cannot be removed; when Donna becomes angry that Rose said she was special but it wasn't her, but the beetle, Rose says that actually they're getting separate readings from Donna that make it seem like reality is bending around her. Donna asks, "What can I do to get rid of it?" to which Rose replies, "You're gonna travel in time."

They prepare Donna, and take her back to the circle of mirrors and technology, with cables running into the TARDIS. At first, Donna thinks she is going to see the creature again and protests, but Rose informs her the mirrors are "incidental", and that they "bounce Chronon energy at the centre, which we control and decide the destination." Donna realises that this is the time machine they will be using. When Donna asks, "How d'you know it's gonna work?" Rose replies "Hmm? Oh, yeah we don't... We're just guessing".

Donna says "I'm ready, 'cuz I understand now, you said I was gonna die but, you mean, this whole world is gonna blink out of existence, but that's not dying, 'cuz a better world takes its place — the Doctor's world. And I'm still alive." Rose remains silent. "That's right, isn't it?" Donna tries to get confirmation of her belief, but Rose only replies sadly, "I'm sorry." Before Donna can learn what will happen, the Lodestone is activated, and she is sent back in time.

Donna lands six months before meeting the Doctor on Monday the 25th, elated that the time travel worked, but quickly realises that she is on Sutton Court, a half a mile away from her past self, and has only got four minutes to prevent her past self from turning right on Little Sutton Street. She tries to run to herself but knows that she will not make it in time. Donna now understands what Rose meant about her death, and she sees a haulage truck coming along that has just passed by her past self at the T-junction. Donna steps in front of the truck, and the driver slams on the brakes. A woman nearby screams at the sight of what happens next...

Before Donna dies, Rose appears and whispers something into her ear to tell the Doctor. At the intersection, Donna's past self decides that instead of sitting in backed up traffic, she will turn left.

As the original timeline reasserts itself, Donna regains consciousness in the fortune teller's stall on Shan Shen, as the Time Beetle on her back releases itself and dies. The baffled and terrified fortune teller flees, screaming, "You were so strong. What are you!? What will you be?!" The Doctor, who has been blissfully unaware of all that's happened, enters and Donna hugs him. When he asks why, she simply replies, "I don't know!" and proceeds to hug him again.

Upon examining the dead beetle, the Doctor tells Donna that it is part of the Trickster's Brigade and that normally it affects one person and the universe compensates, but in Donna's case, it created a parallel universe. The Doctor muses on all of the coincidences surrounding Donna: the fact that she had two parallel worlds that formed around her (this one and the one in the Library) and that he's met her and her grandfather twice. "In the whole wide universe, I met you again," he notes.

The Doctor concludes that they seem to be somehow linked. Donna tells the Doctor she is nothing special, but he counters saying that she's "brilliant". Hearing that triggers Donna's memories of the parallel world and she mentions Rose to the Doctor and her warning about the coming darkness. When Donna mentions that Rose said something about parallel worlds and was blonde, the Doctor starts to realise who Donna saw. When asked if she remembered Rose's name, Donna said she was never told it, but she does remember the two words Rose whispered into her ear: "Bad Wolf". Terrified and now sure of who Donna met, the Doctor runs out into the market square to see the words "Bad Wolf" everywhere: on posters pasted onto the walls, on the ceremonial flags hanging over the market, even on the TARDIS itself (namely the POLICE PUBLIC CALL BOX signs and the instruction plate on the police box's left-hand door). Inside the TARDIS, the control room is glowing red and the Cloister Bell is ringing. When Donna asks what's going on, the Doctor replies, looking horror-stricken, "It's the end of the universe."

Cast

 * The Doctor - David Tennant
 * Donna Noble - Catherine Tate
 * Rose Tyler - Billie Piper
 * Wilfred Mott - Bernard Cribbins
 * Sylvia Noble - Jacqueline King
 * Rocco Colasanto - Joseph Long
 * Capt. Magambo - Noma Dumezweni
 * Fortune Teller - Chipo Chung
 * Mooky Kahari - Marcia Lecky
 * Veena Brady - Suzann McLean
 * Alice Coltrane - Natalie Walter
 * Man in Pub - Neil Clench
 * UNIT Soldier - Clive Standen
 * Jival Chowdry - Bhasker Patel
 * Female Reporter - Catherine York
 * Morgenstern - Ben Righton
 * Spanish Maid - Loraine Velez
 * Studio News Reader - Jason Mohammad
 * Housing Officer - Sanchia McCormack
 * Soldier #1 - Lawrence Stevenson
 * Woman in Doorway - Terri-Ann Brumby
 * Trinity Wells - Lachele Carl
 * Soldier #2 - Paul Richard Biggin

Species

 * The Time Beetle is one of the Trickster's Brigade.

Individuals

 * The Daniels family, Mr and Mrs Obego and Miss Coltrane were also relocated to Leeds.
 * Anne Marie, Cliff and Beatrice are Donna's co-workers.
 * Rose Tyler works with UNIT in Donna's World.
 * On the television news it's mentioned that Sarah Jane Smith used to work for Metropolitan.

Locations

 * Donna turned left on Little Sutton Street heading for Chiswick High Road. In her parallel world, she turned right towards Griffin's Parade.

Companies

 * A truck from Walcott's Haulage passes Donna's car.

Cultural references from the real world

 * The song "Rudolph the Red-Nosed Reindeer" is played.
 * Donna calls Rocco Colasanto (the father of the house) "Mussolini".

Events on the parallel Earth

 * Because Donna wasn't there to convince the Doctor to flee after defeating the Empress of the Racnoss, he drowns in the flooding of the Thames Flood Barrier. He does not regenerate afterward; a UNIT soldier speculates that the Doctor died too fast to do so.
 * Private Harris is at the scene when the Doctor's body is loaded into the ambulance after the Racnoss attack.
 * Martha Jones, Sarah Jane Smith, Maria Jackson, Luke Smith and Clyde Langer all die in Royal Hope Hospital after it is transported by the Judoon to the Moon, though Sarah Jane succeeds in stopping the MRI weapon. Although the Judoon do return to hospital to London, there is only one survivor.
 * The starship Titanic crashes into Buckingham Palace, killing everyone in the greater London area and contaminating southern England. This causes the need for 7000000 people to relocate.
 * The destruction of London triggers a societal collapse in Great Britain, which becomes a police state that closes its borders, and leads to the introduction of concepts such as forced labour camps.
 * The March of the Adipose occurs in America instead of the UK; without the Doctor to stop it, sixty million people are killed (vs one in the original timeline), preventing the US from donating the intended 50000000000 pound relief to Great Britain, and accelerating the UK's decline.
 * Gwen Cooper and Ianto Jones die whilst assaulting the Sontaran warship. Captain Jack Harkness is transported to the Sontaran homeworld.
 * There is no one to prevent the ATMOS devices from decimating the population of the Earth until Torchwood manages to set the gas on fire, although the UK is spared this as, due to the destruction of London, not to mention the lack of petrol, ATMOS never came into widespread use there.
 * The Daleks eventually succeed in detonating the reality bomb (although in this reality, Earth is not one of the planets transported to the Medusa Cascade), beginning the destruction of almost all of creation.

Story notes

 * This is the first story to feature Rose in a starring role since TV: Doomsday.
 * Despite Billie Piper being billed in the opening credits and featuring prominently in the episode, Rose is never referred to by name.
 * Unusually, the episodes featuring Billie Piper were filmed relatively early in the production of the season, which allowed a clip of Rose from this episode to be included in the cinema trailer released in advance of the season being broadcast.
 * This is the "Doctor-lite" episode of the series, similar to Love & Monsters and Blink, albeit with a much darker storyline. Unlike previous Doctor-lite stories, however, the focus is given to the companion, rather than her also taking a minor role. They used the same scheduling trick in the previous episode, Midnight, which featured virtually none of Donna. These episodes allow the production team to complete fourteen episodes, including the Christmas episode in a schedule originally designed to complete thirteen. A second team can be filming the "extra" episode, with the main cast filming only a day or so. Their footage is judiciously spread through the episode to give the impression of a larger interaction, although in the case of Turn Left, David Tennant's participation was restricted to the opening scene and epilogue, with a body double used for the scene where Donna witnesses the Doctor's dead body being loaded into the ambulance.
 * "The bees are disappearing" is quoted again in this episode, this time by Donna's mother, Sylvia Noble. This is a real-world phenomenon, called Colony Collapse Disorder, the incidence of which increased sharply in late 2006, and the cause of which has not been identified. In The Stolen Earth and Journey's End, the cause of the disappearance is revealed.
 * A recurring theme in previous episodes hinted that Donna would die in the future which occurs in this episode. However, this was an alternate reality Donna who sacrificed herself in order to prevent her past self from taking the wrong turn thus forcing her to meet the Doctor as was planned.
 * Part of this episode is filmed in China Town, though not the one in London, but recreated in Cardiff. Chinese people living in South Wales were invited to be background extras via Facebook at the end of 2007. They had to reply to the Doctor Who casting crew with their name and sizes for costumes to be made for them and they were paid approx £70 for the day. David Tennant was seen in "China Town" when he took time out of filming though staying on location to appear on Blue Peter to appeal to viewers to donate shoes to their Shoebiz appeal.
 * Donna is told she can have her fortune told for free because she has red hair. This is a reference to Chinese culture since red is considered very lucky in China. It's also a common carny trick to draw people into the attraction; half off for lovely ladies, men wearing hats, anything that matches some characteristic of the person being appealed to.
 * Graeme Harper's penchant for including a distorted image of a main character is present in this story. Though not included in every single episode he's directed for BBC Wales, it's seen often enough in the majority of his stories to be considered something of a directorial "signature". More typically achieved through the use of refraction (The Unicorn and the Wasp, Army of Ghosts, Journey's End and Utopia), here the motif is continued through the use of reflection. The theme of Donna's multiple worlds is caught through the simple use of mirrors, much as the notion of the investigation was conveyed by the use of magnifying glasses in earlier stories.
 * According to Russell T Davies on Doctor Who Confidential, this episode is the "cheap episode", as he wanted the TARDIS to be on fire, but the budget didn't allow for the effect.
 * Two pieces of background pop music return from other episodes. In the scene in which Donna goes out with her friends to celebrate her new job as Chowdry's personal assistant, the song "Merry Xmas Everybody" by the glam rock band Slade can be heard (first heard on Mickey's radio in The Christmas Invasion). This was also playing during Donna's wedding reception in The Runaway Bride.
 * Billie Pipe r states in the accompanying Doctor Who Confidential episode that she had forgotten how to play Rose and needed to watch past episodes to remind herself.
 * This isn't the first time a Doctor Who story has examined a "What if..." scenario involving the Doctor's influence on a person's life. A similar storyline involved Eighth Doctor companion Sam Jones, depicted in two wildly diverging timelines. (PROSE: Unnatural History)
 * At one point the Nobles and the Italian family take part in a singalong to Queen's "Bohemian Rhapsody". This tune has been the basis for two practical jokes featured on Who franchise-related blooper reels: a group of Sycorax are shown singing it in the Series 2 blooper reel, while the Series 2 gag reel for Torchwood shows the cast cutting up to the same song.
 * When Rose mentions the death of the Torchwood team, a variation on the Torchwood theme music can be heard.
 * Billie Piper's billing in the title sequence has been changed from one line like in Series 1 and Series 2 to two lines, like every other actor credited in that title sequence.
 * The building used as the hotel where Donna and her family spend Christmas is the same building used as Lavender Lawns in The Sarah Jane Adventures serial Eye of the Gorgon.
 * Russell T Davies dropped a subplot involving Donna getting married and having children. This was originally intended to add even more drama to Donna's decision to sacrifice herself and unravel the parallel timeline: not only would she be giving up her own life, but her offspring would be erased from history. However, Davies had now become aware that Steven Moffat had similar plans for Donna in Forest of the Dead and Davies agreed that it was more pertinent to Moffat's tale than his own.
 * Russell T Davies considered exploring how stories set in the past or on other planets would be affected - such as having UNIT send "time commandos" to the year 1599 to foil the plot of the Carrionites in The Shakespeare Code. Ultimately, however, he decided that this would cause an already very self-referential episode to become unnecessarily obsessed with minutiae, and Davies was very concerned about the ability of casual viewers to immerse themselves in the storyline.
 * David Tennant was only required for a day.
 * Catherine Tate was sick with flu during production.

Ratings

 * Official Broadcasters' Audience Research Board (BARB) - 8.09 million viewers. Turn Left was the 4th most watched across all channels on British television for the week.

Myths and rumours

 * The opening credits are reversed, showing the TARDIS moving in the opposite direction in the time vortex. As broadcast and released to DVD, the opening credits are presented normally.
 * It was rumoured that the episode was going to be titled The Doctor's Death.
 * Due to the title, the Sontarans and ATMOS would return. The latter returned and the former were mentioned, but they were not at all the focal point of the story.

Filming locations

 * Bay Chambers, West Bute Street, Cardiff, Wales (Chowdry’s Office)
 * Hunter Street, Cardiff, Wales (The Doctor's dead body is recovered)
 * Clearwater Way, Nant-Fawr Road, Court Road, Heol Gabriel, St Isan Road, Franklin Road in Cardiff, Wales (driving scenes)
 * Lady Mary Allotments, Lady Mary Road, Roath Park, Cardiff, Wales (Wilf sees the stars begin to vanish)
 * The Maltings, East Tyndall Street, Cardiff Bay (Shan Shen Alley)
 * Cardiff Royal Infirmary, Newport Road, Cardiff (News reports of the Royal Hope Hospital vanishing)
 * Egerton Grey Country House Hotel, Porthkerry, Vale of Glamorgan (where Donna and her family went for their Christmas holiday.)
 * Porthkerry Viaduct, Porthkerry, Vale of Glamorgan (when London is destroyed by Titanic’s impact)
 * No. 7 Machen Street, Penarth, Wales (Donna, Wilf and Sylvia discover where they will be staying)
 * Conway Pub, 58 Conway Road, Pontcanna, Cardiff (the crowds run outside the pub to see the star)
 * Mortimer Road, Pontcanna, Cardiff (The Christmas Star attacks London)
 * Sophia Gardens, Cardiff (Rose talks to Donna about her importance)
 * AvestaPolarit Panteg Steelworks, Station Road, Griffithstown, Pontypool, Gwent (Donna and Rose warehouse scenes)

Production errors

 * The sound and shaking of the Royal Hope disappearing is heard before it actually vanishes, whereas in Smith and Jones the sound was heard during the incident.
 * If one looks closely when Rose shows Donna the TARDIS at the UNIT base, the interior of a police box can be seen through the open door instead of the TARDIS interior.
 * When Donna is making the decision to turn right or left, it is clearly raining on the car. However, in any external shots, most notably when Donna has travelled back in time, it is not raining.
 * When Donna is arguing with her boss an explosion is heard and in view, everyone gets up, but in the next camera view, everyone is sitting down and gets up again.
 * Despite the Adipose invasion happening in America within the alternative timeline, the news report shows the same footage taken from Partners in Crime.

Continuity

 * The Trickster previously told Sarah Jane Smith of his intention to use her to locate the Doctor so he could remove him from time and let chaos ensue. (TV: Whatever Happened to Sarah Jane?)
 * This is the second time Rose was present at the death of someone she knew, who also ultimately died to correct the timeline. Rose was present at her father's death, which she prevented when she had come back in time with the Ninth Doctor. The resulting fracture created an alternate timeline and caused chaos until Pete Tyler sacrificed his life to restore the original timeline. (TV: Father's Day) By coincidence, both parallel versions of Pete and Donna are hit by a car, and both die with Rose by their side.
 * The words "Bad Wolf" appear once again as a warning about the end of the universe, sent by Rose as a message for the Doctor. (TV: Bad Wolf / The Parting of the Ways)
 * The Cloister Bell is heard, again as a warning. (TV: Logopolis et al.)
 * Two phrases said by Lucius Petrus Dextrus come to fruition: "There's something on your back" and "She is returning". (TV: The Fires of Pompeii)
 * A UNIT soldier refers to regeneration. UNIT has extensive knowledge of regeneration, having directly been involved with the aftermaths of the regenerations of the Second and Third Doctors. The Brigadier himself is known to have met most of the Doctor's incarnations, and UNIT was also involved with the newly regenerated Tenth Doctor. (TV: Spearhead from Space, Planet of the Spiders, The Christmas Invasion)
 * Much like the Doctor, Rose appears reluctant to be saluted. (TV: The Sontaran Stratagem)
 * The Time Beetle resembles the Eight Legs. They are both arthropods, sit on the backs of humans, and can remain unseen. (TV: Planet of the Spiders)
 * Mirrors were also used for time travel by the Daleks. (TV: The Evil of the Daleks, AUDIO: The Time of the Daleks)
 * A circle of mirrors was also used to expose and reveal the Mara, as is used here to reveal the beetle. (TV: Kinda)
 * There have been a few other instances of the Doctor "dying" and events taking different courses. (PROSE: Blood Heat, COMIC: Final Genesis) The Doctor's apparent death during his eleventh incarnation was actually a fixed point in time, and an alternate timeline was created when attempts were made to prevent it. (TV: The Impossible Astronaut, The Wedding of River Song)
 * When Donna, Wilf and Sylvia are watching the news report, the picture is said to be coming from the Guinevere range of satellites. (TV: The Christmas Invasion)
 * The improbability of the Doctor meeting anyone twice by accident is remarked on. Previous examples of such coincidence are the reunion of the Fifth Doctor and Tegan Jovanka, (TV: Arc of Infinity) and meeting Sarah Jane Smith. (TV: School Reunion) In the cases of Donna and Sarah Jane, the reunion is less improbable than with Tegan because they were both undertaking Doctor-like activities themselves. This subject is brought up again in relation to Donna's grandfather, Wilfred Mott. (TV: The End of Time)
 * Advertisements for Henrik's are plastered on the double-decker buses passing through London during the assault of the Webstar. One bus advertising Henrik's can be seen as a British military tank rolls up and the soldier inside orders troops to fire on the Webstar. (TV: Rose, The Runaway Bride)

Home video releases

 * This story was released in the Series 4 DVD box set in November 2008 along with the rest of the series.
 * It was released as Series 4 Volume 4 with The Stolen Earth and Journey's End.

Behind the scenes

 * According to the invalid source The Time Traveller's Almanac, the opening scene of this episode takes place in the 85th century.