Jack Hawkins

Supt Tom Halliday

John Stratton

Sergeant Ward

Dorothy Alison

Mary Halliday

Sam Kydd

Police Constable in Information Room

Glyn Houston

Detective Sergeant in 'Q' car

Richard Leech

Nightwatchman / Gilson

Geoffrey Keen

Chief Superintendent Jim Malcolm

Sydney Tafler

Stone

Peter Burton

Creasey

George Rose

Slob

Arthur Rigby

Detective Inspector at Chester

Ralph Truman

Colonel Blenkinsop

Ian Bannen

The Young Workman - Stanley James

John Warwick

Detective Inspector at Shipping Office

Joss Ambler

Cashier at Shipping Office

Alec McCowen

House Surgeon

Harry Locke

Secondhand Dealer

Nicholas Parsons

Police Constable Bates

Ursula Howells

Mrs. Elliot / Mrs. Gilson

Meredith Edwards

Mr. Thomas

Harold Goodwin

Official at Somerset House

John Welsh

House Agent at Shepperton

Maureen Delaney

Mrs. Stevens, the daily help

Jameson Clark

Detective Superintendent Ogilvie

William Mervyn

Manager of Festival Hall

Vincent Ball

P.C. at Hospital (uncredited)

Richard Davies

Detective (uncredited)

Frazer Hines

Urchin (uncredited)

Stratford Johns

Constable (uncredited)

David Lodge

Detective at Car Lot (uncredited)

Guy Standeven

Detective (uncredited)

Martin Wyldeck

Officer in Criminal Records Department (uncredited)

Jack McNaughton