Mrs. Louisa Alexandra Wilberforce

Katie Johnson

Professor Marcus

Alec Guinness

Claude, alias 'Major Courtney'

Cecil Parker

Harry, alias 'Mr. Robinson'

Peter Sellers

Louis, alias 'Mr. Harvey'

Herbert Lom

'One-Round'

Danny Green

Lettice (uncredited)

Edie Martin

Detective

Jack Melford

Police Superintendent

Jack Warner

The Barrow Boy

Frankie Howerd

Hypatia

Helen Burls

The Sergeant

Philip Stainton

Constable (uncredited)

Ewan Roberts

Hypatia (uncredited)

Hélène Burls

Cab Driver (uncredited)

Kenneth Connor

Burglar (uncredited)

Michael Corcoran

Parcels Clerk (uncredited)

Harold Goodwin

Junk Man (uncredited)

Fred Griffiths

Miss Pringle (uncredited)

Lucy Griffiths

Constance (uncredited)

Phoebe Hodgson

Security Van Driver (uncredited)

George Hilsdon

Station Master (uncredited)

Vincent Holman

Security Guard (uncredited)

Stratford Johns

Pavement Artist

Leonard Sharp

Second Cab Driver (uncredited)

Sam Kydd

Evelyn Kerry

Policeman (uncredited)

Neil Wilson

(uncredited)

Arthur Mullard

Robert Moore

Radio Car Policeman (uncredited)

George Roderick

Nervous Man (uncredited)

John Rudling

Madge Brindley

Detective at Parcels Office (uncredited)

Peter Williams

Jimmy Charters

Frank Howard

Kathie Johnson

Katie Johnston

Arthur Dibbs

Arthur Howell

Anthony John