Doctor Who: The Armageddon Factor (Part 1)

"The Armageddon Factor (Part One)" is the twenty-first episode of of the sixteenth series of the original British science fiction television programme, Doctor Who. It is the 495th episode of the show overall and the second chapter in the "The Armageaddon Factor" storyline and features Tom Baker as the Fourth Doctor. It was directed by Michael Hayes with a script written by David Fisher. This episode aired on BBC One on Saturday, January 20th, 1979.