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.
Revealing mistake: When the body is in the morgue, his eyes flick left, and then the eyelids move as if to blink.
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)
Continuity mistake: When the body of Glyndwr Michael (Major Martin) is found by fishermen near Huelva, the sun is setting in the west, almost touching the horizon. The shot of the cart wheeling the body towards the town is filmed, judging by the shadows, at about 3 or 4 in the afternoon. (01:17:57 - 01:18:53)
Factual error: All the Royal Naval Volunteer Reserve officers appear to wear green branch distinction cloth ('lights') between their rank rings. Green indicated electrical officers. As non-specialist officers, they shouldn't be wearing any lights at all.
Answer: During Franco's reign, 1938 to 1977, the flag (Rojigualda) had a different coat of arms, the Eagle of St. John, with 'Una Libre Grande' inscribed. It changed in 1945 to a bigger eagle, overall covering some of the red bands of the flag, so, as this is 1943, from what one can see, the flag is correct in the film.
Barndog