4B. The Sontaran Experiment

Season Twelve - 1974/1975

Script Editor: Robert Holmes
Writers: Bob Baker and Dave Martin
Produced by: Philip Hinchcliffe
Director: Rodney Bennett
Designer: Roger Murray-Leach
Incidental Music: Dudley Simpson
Fight Arranger: Terry Walsh (2)


The Doctor, Harry and Sarah trans-mat down from the Nerva beacon and arrive on Earth in the far future. So much time had passed since the solar flares that Earth has returned to a graceful state with no buildings or animals.

On the planet there is also the crew of a crashed spaceship who were slowly being killed. The killer was a Sontaran who was conducting experiments on humans to see the viability of an invasion.

Sarah was also captured and the experiment was to test her fear threshold. The Doctor challenged the Sontaran to a duel, as is the Sontaran custom.

The Sontaran, not used to Earth's gravity, quickly tired, and returned to his ship to re-energise. Harry had been told by the Doctor how to sabotage the Sontaran energy unit, and instead of re-energising the energy fed off the Sontaran.

Regular Cast

  • Sarah Jane Smith: Elisabeth Sladen

Guest Cast

  • Harry Sullivan: Ian Marter
  • Field Major Styre: Kevin Lindsay
  • Krans: Glyn Jones
  • Erak: Peter Walshe
  • Vural: Donald Douglas
  • Roth: Peter Rutherford
  • Zake: Terry Walsh (1)
  • Marshal: Kevin Lindsay (2)
  • Prisoner: Brian Ellis (2)
  • Double for the Doctor: Terry Walsh
  • Double for Harry: Terry Walsh (1)
  • Double for Styre: Stuart Fell (1)

Original broadcast on the BBC

Channel Title Date Viewers Rating
BBC 1 390. Part One Saturday, February 22, 1975 5:30 PM - 5:55 PM 11.0M
BBC 1 391. Part Two Saturday, March 1, 1975 5:30 PM - 5:55 PM 10.5M 55%

Click here to show repeat broadcasts on the BBC

Outside Locations

  • Hound Tor, Nr. Manaton, Devon


Part 2: Watch when the Doctor is fighting with Styre: in the long shots he's standing up straight, but in the close-ups, he's crouched over.

You can see a car in the background of one scene, and there's a farm cottage visible in the background at one point.

Working Titles

The Destructors


Glyn Jones, who here plays Krans, also wrote the novelisation of the Space Museum.