Factual error: When we are in the Colonel's office at the US army base there is a US flag in the corner. It has 50 stars on it, as you can tell by the pattern. There were only 48 stars on the flag during WWII.

Factual error: In the aerial shot over rural Britain near the beginning of the movie, there are two modern cars visible. Too new to be early 40's models.

Continuity: In the scene where Devlin meets Molly for the first time (outside the pub) the ARP sand and water buckets on the wall are in one position. When Molly leaves the scene, just before Devlin enters the pub, the sand and water buckets have changed position.