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Jon Pertwee
The Doctor

Katy Manning
Jo Grant

Nicholas Courtney
Brigadier Lethbridge-Stewart

Richard Franklin
Captain Mike Yates

John Levene
Sergeant Benton

Roger Delgado
The Master

Pik-Sen Lim
Captain Chin Lee

Raymond Westwell
Prison Governor

Michael Sheard
Dr. Roland Summers

Simon Lack
Professor Kettering

Fernanda Marlowe
Corporal Bell

Neil McCarthy
George Patrick Barnham

Clive Scott
Arthur Linwood

Roy Purcell
Chief Prison Officer Powers

Eric Mason
Senior Prison Officer Green

Bill Matthews
Prison Officer