Part One
Series Episode Number: 500World Premiere: Sat 20 Jan 1979 - 6:25pm GMT [BBC One] (United Kingdom)
First Broadcast: Sun 27 Sep 1981 - 11:00pm CDT [WTTW 11 Chicago]
Running Time: 24 minutes 39 seconds
7.50 Million (UK)
Appreciation Index: 65 (UK)Chart Position: 93 () (UK)
Recorded on Sun 05 Nov 1978 in Television Centre 3
Looking for the final segment of the Key to Time, the Doctor and Romana arrive on the planet Atrios which is in a major nuclear war with the neighbouring world of Zeos.