Donald Gray

Extra (uncredited)

Peter Burroughs

TV Program Announcer (uncredited)

William Peck

Robert Maitland

Captain Ross

Young Yacht Guest (uncredited)

Polly's Husband (uncredited)

Captain White / Captain Black / The Mysterons (voice)

Ted Fleming

James Martin

Col. George Gordon

Jimmy Thompson

Headmaster

Inspector Wills

Colonel White / Captain Black / The Mysterons (voice)

Stukely

Don (as Eldred Tidbury)

Albert de Courcey

The Mysterons / Colonel White / Captain Black (voice)

Paul Merton

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The Mysterons / Colonel White / Captain Black (voice)

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Father Conrad