Factual error: When Aston Kutcher is getting the first text from Natalie Portman, you can see his iPhone is showing June 12 on the lock screen as the current date. The text from Emma have also a date of "06/12/10" next to it within Messages app. On iPhone, the texts received on the same day should only show time at which message arrived, and not a date.
Factual error: During scenes set in the early Noughties (one of Dex and Emma talking on a rooftop at night, and another of Dex crossing the river on a bus), modern buildings are shown on the skyline, including the Heron Tower (2009), the tallest building in the City at the time of filming, but it didn't exist at the time the scene is set.
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.
Factual error: Driveway cut outs with tapered edges were not extant during the time period of this film.