At the end of 1969, Doctor Who faced a very uncertain future. Ratings had slumped and Patrick Troughton had left the show. In a brave move, producer Derrick Sherwin re-invented the show as a fast-paced, Earth-bound colour series for the 1970s. Cast and crew look back at the making of this story and how a strike at the BBC studios inadvertently created the only classic series story to be made entirely on film. With actor Jon Pertwee, producers Derrick Sherwin and Barry Letts, script editor Terrance Dicks, costume designer Christine Rawlins and assistant script editor (and inadvertent Auton actor) Robin Squire.