From the Radio Times:

7.35-8.00
Doctor Who
starring Sylvester McCoy
with Bonnie Langford
in Time and the Rani
The last of a four-part story
by PIP AND JANE BAKER
Catalyst (noun): vital substance which allows a chain of events to proceed
Countdown (noun): announcement of the last remaining seconds before something takes place
Armageddon (noun): the end of the world
Incidental music KEFF MCCULLOCH
Lighting HENRY BARBER
Script editor ANDREW CARTMEL
Designer GEOFF POWELL
Producer JOHN NATHAN-TURNER
Director ANDREW MORGAN
★ CEEFAX SUBTITLES