Donald Gray

as The Mysterons / Colonel White / Captain Black (voice)

as Captain White / Captain Black / The Mysterons (voice)

as Colonel White / Captain Black / The Mysterons (voice)

as Polly's Husband (uncredited)

as Inspector Wills

as Extra (uncredited)

as Headmaster

as Captain Ross

as Col. George Gordon

as TV Program Announcer (uncredited)

as Robert Maitland

as Jimmy Thompson

as William Peck

as Stukely

as Peter Burroughs

as Ted Fleming

as James Martin

as Albert de Courcey

as Chauncey (as Eldred Tidbury)

as Don (as Eldred Tidbury) (uncredited)

as Young Yacht Guest (uncredited)

as Father Conrad

as Sir John Brinder

as The Mysterons / Colonel White / Captain Black (voice)

as Paul Merton

as Mark Saber