5F. The Armageddon Factor

Season Sixteen - 1978/1979 (The Key To Time)

Script Editor: Anthony Read
Writers: Bob Baker and Dave Martin
Produced by: Graham Williams
Director: Michael Hayes
Designer: Richard McManan-Smith
Incidental Music: Dudley Simpson


The trail for the Key to Time is near an end, and there is only one more segment to find. As they have had no dealings with the Black Guardian, the Doctor is warned that this may be when they meet him.

The TARDIS materialises in an underground labyrinth on Atrios. Atrios is at war with a neighbouring planet, Zeos. Casualities are high, and the medical centre is up to full capacity. Princess Astra is always keen to help the victims, and she does not agree with the Marshall.

Every fleet the Atriosans send up always gets destroyed, and Zeos almost seems unharmed. The Doctor says he can help, and says he can build a psychological barrier that would make the Zeons not want to attack Atrios. For that he must have a Zeon prisoner to test. The Marshall says that in war there are no prisoners, but it is strange that no-one recalls seeing a Zeon.

The Black Guardian has a servant, the Shadow, who is on a hidden third planet in between. The Doctor is led to the third planet and encounters an old friend, Drax, who built Mentalis, the Zeon computer, to fight the war.

With Drax's help the Doctor escapes from the Shadow with Romana. Princess Astra is the final segment of the Key to Time, and when the Key is assembled the Doctor has power over ALL time.

The Black Guardian appears as the White Guardian, although the Doctor tricks him into revealing his identity. The Doctor says that the Key is too powerful for any one being, or any Guardian, and orders it to split up, where all the pieces return to their original states.

Regular Cast

  • Voice of K-9: John Leeson
  • Romana: Mary Tamm

Guest Cast

  • Princess Astra: Lalla Ward
  • Marshal of Atrios: John Woodvine (2-3)
  • Major Shapp: Davyd Harries (1-4,6)
  • Surgeon Marek: Ian Saynor (1-4,6)
  • "Hero": Ian Liston (1)
  • "Heroine": Susan Skipper (1)
  • Guards: John Cannon (1), Harry Fielder (2)
  • The Shadow: William Squire (3-6)
  • Pilot: Pat Gorman (3-4)
  • Technician: Ian Armstrong (3)
  • Drax: Barry Jackson (5-6)
  • Mute: Stephen Calcutt (5-6)
  • The Black Guardian: Valentine Dyall (6)
  • Patients: (all 1) Frank Arbisman, Barbara Hampshire, Juliet St Davis, Ian Sheridan, Terry Ward, Albert Welch
  • Nurses: Val McKinnon (1), Judy Roger (2)
  • Voices: Ian Liston (2)
  • Guards: (all 1-3) Peter Caton, Tony O'Leary, Peter Roy, Richard Sheekey, Barry Summerford, Reg Turner
  • Technicians: (all 1-3) Peter Bithiel, Constance Carling, Gerry Dean, Bill Hughes, Malcolm Ross, David Wilde
  • Mutes: Michael Braben (3-6), James Haswell (3-4), Ridgewell Hawkes, Danny Rae (3-4), Derek Suthern (5-6)
  • Extras: Michael Gordon-Brown (6), Eddie Whiting (3-6)

Original broadcast on the BBC

Channel Title Date Viewers Rating
BBC 1 500. Part One Saturday, January 20, 1979 6:25 PM - 6:50 PM 7.5M 65%
BBC 1 501. Part Two Saturday, January 27, 1979 6:25 PM - 6:50 PM 8.8M
BBC 1 502. Part Three Saturday, February 3, 1979 6:25 PM - 6:50 PM 7.8M
BBC 1 503. Part Four Saturday, February 10, 1979 6:25 PM - 6:50 PM 8.6M
BBC 1 504. Part Five Saturday, February 17, 1979 6:20 PM - 6:45 PM 8.6M
BBC 1 505. Part Six Saturday, February 24, 1979 6:30 PM - 7:00 PM 9.6M 66%


  • Ealing Film Studios
  • Television Centre Studio 3

Working Titles