Alec Guinness

Professor Marcus

Cecil Parker

Claude, alias 'Major Courtney'

Herbert Lom

Louis, alias 'Mr. Harvey'

Peter Sellers

Harry, alias 'Mr. Robinson'

Danny Green

'One-Round', alias 'Mr. Lawson'

Katie Johnson

Mrs. Wilberforce

Jack Warner

The Superintendent

Philip Stainton

The Sergeant

Frankie Howerd

The Barrow Boy

Madge Brindley

Large Lady (uncredited)