Factual error: At the beginning of the film, as a British Admiral (or senior naval officer) leaves Bletchley he returns a salute. Although a naval officer, he does not give a naval salute but rather a half hearted army salute.
Factual error: The scene of 1946 London - Trafalgar Sq. looking south down Whitehall. You can see the turrets of the new MP office building - put up only a few years ago.