Alec Guinness

Character: Professor Marcus

Cecil Parker

Character: Claude, alias 'Major Courtney'

Herbert Lom

Character: Louis, alias 'Mr. Harvey'

Peter Sellers

Character: Harry, alias 'Mr. Robinson'

Danny Green

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

Katie Johnson

Character: Mrs. Wilberforce

Jack Warner

Character: The Superintendent

Philip Stainton

Character: The Sergeant

Frankie Howerd

Character: The Barrow Boy

Madge Brindley

Character: Large Lady (uncredited)

Hélène Burls

Character: Hypatia (uncredited)

Kenneth Connor

Character: Cab Driver (uncredited)

Michael Corcoran

Character: Burglar (uncredited)

Harold Goodwin

Character: Parcels Clerk (uncredited)

Fred Griffiths

Character: Junk Man (uncredited)

Lucy Griffiths

Character: Miss Pringle (uncredited)

George Hilsdon

Character: Security Van Driver (uncredited)

Vincent Holman

Character: Station Master (uncredited)

Stratford Johns

Character: Security Guard (uncredited)

Sam Kydd

Character: Second Cab Driver (uncredited)

Edie Martin

Character: Lettice (uncredited)

Jack Melford

Character: Detective (uncredited)

Arthur Mullard

Character: (uncredited)

Ewan Roberts

Character: Constable (uncredited)

George Roderick

Character: Radio Car Policeman (uncredited)

John Rudling

Character: Nervous Man (uncredited)

Leonard Sharp

Character: Pavement Artist (uncredited)

Peter Williams

Character: Detective at Parcels Office (uncredited)

Neil Wilson

Character: Policeman (uncredited)

Phoebe Hodgson

Character: Constance (uncredited)