Doctor Who: The Armageddon Factor

The final segment of the Key to Time is at the heart of a devastating war between neighbouring planets Atrios and Zeos. The Fourth Doctor discovers that a sinister entity is manipulating events and the cost of obtaining the final segment may be more personal than he imagined.

Cast: Tom Baker, Mary Tamm, John Leeson, John Woodvine, Lalla Ward, Davyd Harries