Jon Pertwee as The Doctor

Katy Manning as Jo Grant

Nicholas Courtney as Brigadier Lethbridge-Stewart

Roger Delgado as The Master

Nicholas Pennell as Winton

John Ringham as Ashe

David Webb as Leeson

Sheila Grant as Jane Leeson

Roy Skelton as Norton

Helen Worth as Mary Ashe

John Line as Martin

Mitzi McKenzie as Mrs. Martin

John Scott Martin as Robot

Pat Gorman as Primitive / Voice / Long / Colonist

Graham Leaman as Time Lord

Peter Forbes-Robertson as Time Lord

John Baker as Time Lord

Bernard Kay as Caldwell

Morris Perry as Captain Dent

Tony Caunter as Morgan

John Herrington as Holden

Stanley McGeagh as Alien

John Tordoff as Alec Leeson

Norman Atkyns as The Guardian

Roy Heymann as Alien Priest