Scotland Yard detectives attempt to solve a spate of safe robberies across England beginning with clues found at the latest burglary in London. The film is notable for using a police procedural style made popular by Ealing in their 1950 film The Blue Lamp. It is known in the US as The Third Key.

Jack Hawkins
as Supt Tom Halliday

John Stratton
as Sergeant Ward

Dorothy Alison
as Mary Halliday

Michael Brooke
as Tony Halliday

Sam Kydd
as Police Constable in Information Room

Glyn Houston
as Detective Sergeant in 'Q' car

Richard Leech
as Nightwatchman / Gilson

Newton Blick
as Deputy Commander

Geoffrey Keen
as Chief Superintendent Jim Malcolm

Sydney Tafler
as Stone
John Chard
The key is to follow the key! The Long Arm is directed by Charles Frend and written by Janet Green and Robert Barr. It stars Jack Hawkins, John Stratton, Dorothy Alison and Michael Brooke. Music is by Gerard Schurmann and cinematography by Gordon Dines. Detective-Superintendent Tom Halliday (H...