Factual error: When Johnny and Lorna are in the sushi bar, Lorna says 'cheers' in Japanese to Johnny before drinking Japanese sake. (An English subtitle is displayed). Johnny, obviously not knowing what he is saying replies in Japanese, and an English subtitle is displayed saying 'may all of your daughters be born with three bottoms'. The actual translation for what he says is 'May all of your daughters be born with a small penis'. (Not that any normal person would notice) (00:36:15)
Factual error: When Johnny lands in the hospital instead of Sauvage's headquarters, there is a sign behind him which uses the American spelling of "Orthopedics" instead of the British "Orthopaedics."
Factual error: At the end of the film, after Johnny has foiled Sauvage's plot and the Queen has been restored, a news announcer says that Sauvage has been charged with high treason, which still carries the death penalty. Assuming the film is set in 2003, this is incorrect since the death penalty in Britain was abolished for all crimes, including treason, by the Crime and Disorder Act passed by Parliament in 1998.
Factual error: After the Crown Jewels have been stolen Bough and Johnny arrive at what is supposedly the Tower of London (where the Jewels were stolen from). They actually drive up to the entrance of King's College London on Chancery Lane. Even if they couldn't get permission to film at the real Tower, why pick such a well known building as a replacement?
Factual error: Sauvage's headquarters are supposed to be in the City of London, but in one shot scanning from the top to the bottom of the building, a road sign saying "Canada Square" is visible. This is on Canary Wharf, in the Docklands.
Factual error: All monarchs of England are crowned in Westminster Abbey; nearly every monarch since Edward II has been crowned while sitting on the coronation chair with a large stone known as the Stone of Scone (or Stone of Destiny) resting beneath it. This stone was stolen from the Scots in 1496 and given back to them 500 years later, in 1996, but will presumably be loaned back to the English for future coronations. The building in which Sauvage's coronation was being held was not Westminster Abbey, the throne he was sitting in was not the coronation chair, and the Stone of Destiny was not resting under the chair. Trivial points, perhaps, but factual errors all the same. They could have least have made them look the same.