Jon Pertwee as The Doctor

Katy Manning as Jo Grant

Nicholas Courtney as Brigadier Lethbridge-Stewart

Richard Franklin as Captain Mike Yates

John Levene as Sergeant Benton

Roger Delgado as The Master

Michael Wisher as Rex Farrel

Harry Towb as McDermott

David Garth as Time Lord

Frank Mills as Radio Telescope Director

Christopher Burgess as Professor Philips

Andrew Staines as Goodge

John Baskcomb as Rossini

Dave Carter as Museum Attendant

Stephen Jack as Farrell Senior

Barbara Leake as Mrs. Farrell

Roy Stewart as Strong Man

Dermot Tuohy as Brownrose

Norman Stanley as Telephone Mechanic

Terry Walsh as Auton Policeman

Pat Gorman as Auton Leader

Hayden Jones as Auton (voice)

Tommy Reynolds as Troll Doll (uncredited)