From the Radio Times:

5.50 Colour
Dr Who
starring
Jon Pertwee
The Mutants
by BOB BAKER
and DAVE MARTIN
Part 2
Jo is a hunted fugitive on the poisonous surface of Solos.  The Marshal blackmails the Doctor into helping him with his plans.
Title music by RON GRAINER
and the BBC RADIOPHONIC WORKSHOP
Incidental music by TRISTRAM CARY
Script editor TERRANCE DICKS
Designer JEREMY BEAR
Producer BARRY LETTS
Director CHRISTOPHER BARRY