Other mistake: The body of a man is dropped from a plane into the sea with fake documents to mislead Germans. To convince the enemy that he's a soldier, cause of death needs to pass for drowning. The first drowned corpse viewed has no legs, so Firth keeps looking. He's told that a man who took rat poison to end his life is a good fit since the poison is undetectable. However, no mention is made of the fact that there is no sea water in his lungs - something any coroner would discover. (01:43:40)
Factual error: When Fleming salutes Cholmondeley and Montague, they return the compliment whilst not wearing their headdress. Members of the British armed forces never salute if they are not wearing a hat, instead they would stand to attention.