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The Sontaran Experiment was the third serial of season 12 of Doctor Who. Shot entirely on location, it was the shortest story of the 1970s, with only two episodes. An outdoor shoot, all scenes were unusually recorded on videotape rather than film.

Script editor Robert Holmes was not a fan of six-part stories, believing that they were padded, so for season twelve, he decided to have one four-part story and one two-part story. With Christopher Langley's "Space Station" already in the works, he looked to Baker and Martin to fill the gap. As an outline, Holmes asked them to set it on Earth and bring back the Sontarans. This would help them capitalise on the costly ship interior and Sontaran costume used in The Time Warrior.

Baker and Martin were commissioned to write the script on 23 May and asked to deliver episode one shortly after, on 5 June. Part two was in by 6 July and Holmes re-wrote it extensively, removing a sub-plot in which Vural was revealed to be a victim of mind-control. Despite Holmes' earlier intentions, a new Sontaran costume was made for Kevin Lindsay.

During filming, Tom Baker slipped and broke his collarbone. Believing the injury to be more serious, producer Philip Hinchcliffe had designer Roger Murray-Leach drive Baker to the nearest hospital. Worried that he might have to recast his new star, Hinchcliffe was relieved when the injury turned out to be much less serious than first thought, with Baker able and willing to continue filming the next day. The scarf the Doctor wore covered Baker's neck brace, but fight arranger Terry Walsh did end up doubling for Baker in several shots. (INFO: The Sontaran Experiment)

This story started a very short story arc of the Doctor, Sarah and Harry trying to return to Nerva to get back to the TARDIS, but being interrupted. They would return in Revenge of the Cybermen, albeit hundreds of years prior to when they had originally arrived.


Arriving on a seemingly deserted Earth, the Doctor, Sarah and Harry soon discover a crew of shipwrecked astronauts from a distant Earth colony. Lured there by a fake distress call, the astronauts are being experimented on by the deadly Sontarans in preparation of a full-scale invasion of the planet. Can the Doctor defeat Sontaran Field-Major Styre and save the world?


Part 1[]

The Fourth Doctor and his companions Sarah Jane Smith and Harry Sullivan transmat down from Space Station Nerva to a field on the now-healed Earth. The Doctor starts fixing the circle of transmat refractors with his sonic screwdriver while the others wander off to explore.

"What you're actually saying is: you're busy and you'd like us to push off."

As they walk across the plain, Sarah hears a sound and sees movement on the top of a hill. Harry dismisses it. Two men in spacesuits, Erak and Zake, are observing the Doctor through the crosshairs of their rifles. Erak leaves Zake to watch the Doctor while he reports the presence of the Doctor to another man in a spacesuit, Krans, who is tending a campfire. Meanwhile, Harry slips on the edge of a hole and tumbles into it. He is stuck, unable to climb out. Sarah observes that the edge of the hole had been covered deliberately. Harry has no choice but to stay put as Sarah goes to fetch the Doctor.

Zake's observation of the Time Lord is interrupted by a strange floating robot that bears down on him. Zake flees, the robot pursuing him over the edge of a cliff, where he falls to his death. The Doctor finds Zake's body when Erak and Krans arrive. Thinking the Doctor has killed Zake, they stun him with their rifles before he can explain. As they carry the unconscious Doctor away, they are watched by yet another spaceman, Roth.

Sarah gets back to the circle to find the Doctor gone, his screwdriver abandoned. When Sarah returns to the hole, Harry is nowhere to be seen. Something had started throwing rocks down at Harry and, in scrambling for cover, he found a way out of the hole, climbing through some rocks to the hills beyond. Sarah is about to climb down into the hole to look for Harry when Roth grabs her from behind, hiding her as the drone floats past. Once the danger is gone, Roth introduces himself to Sarah. It was he who covered the edge of the hole, trying to trap the drone. He tells Sarah that the robot serves an alien who lives among the rocks, an alien who has tortured him and killed two of his crew. Roth is obviously traumatised by his experiences. He vows he will not be captured again. When Sarah tells him about her friends, he informs her that the Doctor has been taken to the campsite.

Erak and Krans interrogate the Doctor.

At the campsite, Erak and Krans interrogate the Doctor, demanding to know what he has done to their crewmates. When the Doctor explains that he came down from Space Station Nerva, the spacemen (now joined by their leader, Vural) greet that news with great scepticism. Nerva, the lost colony of mankind, is a mere legend, like Atlantis. The spacemen are from one of the colonies, GalSec. The Doctor suddenly spots an odd looking button on Vural's suit, identifying it as non-human technology. The button is actually a remote camera. Somewhere else, everything is being observed by something with a grey, heavy, four-fingered hand.

Roth brings Sarah near the campsite but refuses to approach; he tells Sarah he saw Vural go to the rocks and the alien let Vural go. The GalSec men tell the Doctor that a GalSec freighter had gone missing. Detecting a distress signal from the supposedly uninhabited Earth, they came to investigate, but their ship was vaporised when they emerged, leaving nine of them stranded. The surviving crew began to vanish one by one. The Doctor offers to fix the transmat refractors and beam them all to Nerva, where they can contact another GalSec ship, but Vural says that they are not taking orders from the "Old People". While the Nervans did nothing but sleep, the rest of mankind had spread across the galaxy and built an empire. At this point, Roth appears. While the three spacemen chase him, Sarah sneaks out from the rocks and frees the Doctor.

Roth loses the others and meets up with Sarah and the Doctor. Sarah tells the Doctor about the robot, and the Doctor examines some residue on the ground, evidence of a terullian drive, except there is no terullian in this galaxy. The Doctor reasons that there must be some way out of the hole that Harry fell in, but as he climbs down, he too slips and falls to the bottom, losing consciousness. At that moment, the robot returns and snares Roth and Sarah with cables.

Harry has made it to the hills, where he spots a man-sized metal sphere among the rocks. As he watches, the robot arrives with Roth and Sarah in tow. The sphere's door opens and to Sarah's horror, out steps a Sontaran warrior.

Part 2[]

Styre examines the results of Experiment 5: Fluid deprivation

When Sarah expresses her disbelief, the Sontaran tells her he is Field Major Styre of the Sontaran G3 Military Assessment Survey, identical to the other Sontaran clone she encountered, but not the same. Roth cries out that he will not be tortured again and makes a break for it, only for Styre to shoot him down. Roth had already been tested, so he was of no further use to Styre. Sarah, however, is far more interesting.

The three spacemen find the Doctor down the hole, but as they force him to climb out at gunpoint, the drone arrives and snares the trio. The Doctor goes back to the bottom of the hole. He finds the same exit that Harry used. Harry, in the meantime, finds another human chained to the side of the rocks, severely dehydrated.

Nearby, Styre has Sarah tied up to the rocks as well and has placed a device on her forehead. He seals her in with a force field. Styre goes to his transmitter station and reports to his Marshal. The Marshal is impatient for the intelligence report, but Styre tells him that some inconsistencies have arisen that he has to clear up before he submits it. Styre proceeds to subject Sarah to Experiment 7: resistance to fear. The device on her head begins to give Sarah hallucinations, and she starts to panic. The Doctor, however, has reached her and uses the sonic screwdriver to breach the force field. When he rips off the device on her forehead, she gives a scream and falls unconscious. The Doctor, enraged, attacks Styre, but the Sontaran easily fends him off. Styre shoots him when he runs, the Doctor collapsing in a heap.

Harry finds Sarah, unconscious, and the Doctor's apparently lifeless body. The chained-up spaceman has also died of thirst and Styre records the result of Experiment 5: human resistance to fluid deprivation. Harry prepares to attack Styre from behind but is dragged back by the Doctor. Styre's shot had hit a piece of scrap metal the Doctor had taken from Nerva, saving his life. The Doctor tells Harry to look after Sarah while he discovers Styre's mission.

The robot brings the three remaining spacemen to Styre's ship, where it turns out that Vural had tried to make a deal with Styre in exchange for his own life. However, Styre intends to experiment on Vural anyway, this time to determine the human ribcage's resistance to pressure and muscular strength. He forces Erak and Krans to hold a gravity bar above Vural's body, making it progressively heavier until it is all they can do to keep it from crushing Vural. Styre stops the experiment temporarily to go make another report and the Doctor eavesdrops on it.

The Doctor sneaks away again and meets Sarah and Harry. He tells them that Earth's galaxy has somehow become strategically important in the Sontarans' never-ending war against the Rutans. Styre's experiments are to determine the physical limitations of humans, following which a Sontaran fleet will invade. The Doctor hatches a plan: he will distract Styre by challenging him to single combat. After a while, Styre will tire and return to his ship to recharge his energy. While the Doctor fights Styre, Harry will go to Styre's ship and remove a key component.

Styre's experiment is disrupted when the Doctor challenges him.

The Doctor confronts Styre, lying to him that his experiments are useless: the spacemen are the humans' "slave class", the weakest of them all. The Doctor, on the other hand, is representative of the warrior class. Styre accepts the Doctor's challenge. While the two fight, Sarah and Harry free the three spacemen, then Harry climbs towards Styre's ship to carry out the Doctor's instructions. Styre nearly gains the upper hand, but Vural attacks him, saving the Doctor at the cost of his life. Styre reaches his limits and heads back to his ship. As the time travellers back away from Styre's ship, the Sontaran staggers out in pain, shrivelling and deflating like a balloon before exploding.

The Doctor explains that the device Harry removed sabotaged the energiser, so the energy fed on Styre instead of the other way around. The Doctor makes his way to Styre's transmitter. He tells the Marshal that not only has Styre's intelligence mission failed, but that the invasion plans are in their hands. If the Sontaran fleet moves across the buffer zone, it will be destroyed. The Marshal swears revenge and terminates the signal.

Erak and Krans thank the Doctor but decide to wait on Earth for the Nervans rather than transmat up to the station. As they watch, Sarah, Harry and the Doctor vanish.



Uncredited crew[]


Cultural references from the real world[]

  • Harry says he feels "a bit like a Morse message" after the broken teleportation from Nerva.
  • Styre calls the Doctor a "worm".

The Doctor[]

The Doctor's items[]

Earth locations[]


Styre's experiments[]

  • Experiment 4 discovers that immersion in the fluid H2O produces asphyxiation.
  • Experiment 7 concerns resistance to fear: Sarah is caused to hallucinate a snake, rocks closing in on her, and sludge creeping up her legs.
  • Experiment 8 requires Krans and Erak to keep a gravity bar from crushing Vural.


  • The piece of metal which saves the Doctor's life was a synestic locks from Nerva's shuttle, which he removed and pocketed while on Nerva.

Story notes[]

  • This serial immediately follows the events of the previous serial, The Ark in Space.
  • The working title for this story was The Destructors. (REF: The Fourth Doctor Handbook)
  • Although the serial was the third to feature Baker, it was actually the second shot, hence the out-of-sequence production code.
  • This was only the second serial in the history of Doctor Who (the first being 1970's Spearhead from Space) to be shot entirely on location, in this case on Dartmoor. However, unlike Spearhead from Space and the location material for other serials, the production was mounted entirely on videotape using an Outside Broadcast unit, rather than on film, as was more usual for the time.
  • During shooting, lead actor Tom Baker broke his collarbone. However, because part of his costume was a large scarf, he could conceal the neck brace he had to wear following the injury. For action scenes, he was doubled by regular stunt performer Terry Walsh, shot from several face-concealing angles.
  • This was the first two-part serial to be broadcast since 1965's The Rescue and the last until 1982's Black Orchid.
  • Kevin Lindsay is credited as "Styre" for part one. For part two, he is billed as "Styre and the Marshal" on-screen and as "Styre/The Marshal" in Radio Times.
  • This was the first story to contain no interior (i.e. studio) scenes.
  • Glyn Jones, who played the astronaut Krans, wrote the First Doctor serial The Space Museum, making him one of five individuals to have both written for and acted in Doctor Who (the others being Victor Pemberton, Derrick Sherwin, Mark Gatiss, and Toby Whithouse).
  • Kevin Lindsay makes his last Doctor Who appearances, playing Styre and his superior, the Marshal — who appears only on a video screen. He died not long afterwards as a result of a long-standing heart condition.
  • The GalSec astronauts were mostly played by South African actors who used their native accents. Bob Baker and Dave Martin were interested in how language evolves with cultural cross-pollination and believed the cultural and racial mix of South Africa was an indication of how language might sound in the future.
  • This is one of only eleven televised stories in the history of Doctor Who not to feature the TARDIS at all, along with Mission to the Unknown, Doctor Who and the Silurians, The Mind of Evil, The Dæmons, The Sea Devils, Genesis of the Daleks, Midnight, The Lie of the Land, The Woman Who Fell to Earth and Ascension of the Cybermen.
  • Bob Baker and Dave Martin wanted to incorporate some relics of human civilisation which would imply that the story was actually set where London had once stood — for instance, by having the top of Nelson's column poking up out of the ground in homage to Planet of the Apes. Much of the action of their scripts was set in the ruins of an old priory, and so many of Styre's torture devices were medieval in nature. Robert Holmes rewrote episode two extensively, in the process removing a subplot in which it would have been revealed that Styre was controlling Vural's mind.
  • Bob Baker and Dave Martin were unhappy with the title, as it spoiled the identity of the villain.
  • Robert Holmes gave Bob Baker and Dave Martin a three-hour brief on Sontaran culture, including their sex lives. All they wanted to know was that "he was a squat, froggy thing".
  • Rodney Bennett claimed that he suggested the Doctor always had junk and bits of string in his pockets, as well as the yo-yo.
  • Filming on Dartmoor was hampered by nonstop rain and the crew had to drag heavy cameras around.
  • Sarah is the only female character in this story.


  • Part one - 11 million viewers
  • Part two - 10.5 million viewers

Filming locations[]

  • The entire serial was filmed over seven days at Dartmoor National Park in Devon.
  • The major location was Hound Tor, Manaton, Dartmoor.

Production errors[]

If you'd like to talk about narrative problems with this story — like plot holes and things that seem to contradict other stories — please go to this episode's discontinuity discussion.
  • During the fight, Styre's head is knocked sideways. When Styre touches his suit, his head wobbles.
  • A crew member can be heard briefly from off-screen giving the cue to drop rocks in the trap that Harry falls into.
  • There is a shot around 15:30 in part one where the robot turns its head around, and the crewmembers are reflected off the shiny metal.
  • Sarah calls Styre and Linx "identical" — despite the fact they clearly have different designs.


DVD, video and other releases[]

DVD releases[]

This story was released as Doctor Who: The Sontaran Experiment (Special Value Edition) - one of the few occasions in which a two-episode story has been released by itself.




Boxset release[]

This story was released in the Bred for War DVD boxset on 5 May (Region 2) and 8 July (Region 4) alongside all the classic series Sontaran stories. The DVD is the same as the one sold separately. In 2018 the story was released as part of a Doctor Who Season 12 bluray box set. The initial box set released in the UK included deluxe package and collector pictures, while the US release was release in normal packages with no cards.

VHS releases[]

This story was released in October 1991 as a double video, together with Genesis of the Daleks.

Digital releases[]

  • The story is available for streaming in the US through Hulu Plus or Amazon Instant Video in the UK.

External links[]