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)
