- HD 1080
- Runtime: 96m.
- Status: Released
- 1
- Languages: en
- Country: United Kingdom
- Director: Charles Frend
- Stars: Jack Hawkins, John Stratton, Dorothy Alison, Michael Brooke, Sam Kydd
- keywords: detective, scotland yard, film noir
- Production_studio: Ealing Studios
- Slogan: The True Inside Story of Scotland Yard's Crime Busters!
- The The Long Arm is featured in the top rankings of 1956
- #6 in Top Crime Movies of 1956
- #9 in Top Thriller Movies of 1956
- #2 in Top Mystery Movies of 1956
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.