Factual error: The scene showing Paris at night displays heavy traffic and bright car headlights over the distance. Both were not possible to be seen at time the story occurs, circa 1920's.
Factual error: Josh abseils forwards into the cave and in the next shot is seen coming alongside Victoria, in the standard seated abseil position. This would not have been possible, due to the design of his harness, without moving his abseil device from his back to his front. This would have involved him removing the device completely and then re-attaching it to the front of his harness which would be impossible during descent. (00:15:20)
Factual error: Rochester Castle is seen standing alone and isolated from any other settlement. In actual fact it stands on the edge of the City of Rochester and very close to Rochester Cathedral, both of which certainly existed at this time.
Factual error: On the plane, Emma shows an issue of Hello! magazine featuring the heiress Grace is passing as. It's labeled as "number 1100, May 31 2010", but the May 31 2010 issue was actually number 1125. (00:30:30)
Factual error: When D'artagnan and the musketeers are infiltrating the Tower of London, the king's guards are seen with the Tudor Rose crest on their tunics. By the time stated at the beginning of the movie, the last Tudor monarch (Elizabeth I) had been dead for 80+ years.