Factual error: Reference the rural scenes. In the 40s, barley fields did not exhibit large perpendicular tracks made by crop sprayers.
Factual error: At the end of the film, Tom Jericho makes his way to the "Adelphi Hotel" in Manchester. The outside of the Adelphi building just off the Strand in London is used.
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.
Factual error: In the opening scenes the staff car door is opened by a four-ringer Wren (Deputy Director, very rare) equivalent to Royal Navy Captain, instead of a rating.