Continuity mistake: When XXXX is awakened by Dragan's phone call, there is a gun lying on his pillow. In the overhead shot the gun is pointing in one direction; in subsequent shots it is pointing the other way.
Revealing mistake: When Gene's bodyguard (the one with the moustache) shoots Slasher and Duke, just before Slasher is shot the bullet hole effect is visible on her forehead (sightly concealed by make-up) just before the actual 'shot'.
Factual error: The scene at the start of the film shows XXXX and his assistant making drugs. In the voice-over, XXXX mentions that his assistant has a double first in industrial chemistry from Cambridge, and is doing this job to pay off his student debt. This is wrong on a number of levels. First of all, there is no such subject as industrial chemistry to study at Cambridge, nor has there ever been such a subject. Only Chemistry is taught. Secondly, Chemistry is a single honours subject: you would only get at best a first in it, not a double first. "Double first" means you scored top marks in two separate subjects you study - for example if you read French and Spanish together, that would be double honours. This is not the case however for chemistry. Lastly, the statement about paying off student debt makes no sense given the film was set in Britain. At the time, student fees were no more than £3000 a year ($3800) so in a four year course you would end up paying only £12000 ($15200), plus living expenses. But loans are only repaid once you're earning above a certain limit, and then proportionally to your income - they're not "due" like a standard loan. It therefore makes no sense for the assistant to be working such a dangerous and illegal job if all he wishes to do is pay off his student debt - he has evidently worked with XXXX for a long time given how much XXXX trusts him.
Revealing mistake: When XXXX is in Greenwich Park with Mr. Lucky and he gets shot, Dragan shoots at the grass in front of XXXX. Grass is thrown into the air, and you can see white smoke coming from an explosive for the special effects.
Continuity mistake: When XXXX is dropped off by Eddie Temple he is wearing a dressing gown, but the next shot is of him in his kitchen pouring a drink wearing a T-shirt and jacket, all worked up and agitated by the news he's just heard.
Continuity mistake: In the scene in the park where XXXX and Lucky are waiting in the bush - when Lucky looks through his telescopic sight at Dragan it appears to be raining, however, when we return to the wide shot of the two of them in the bush, it appears to be a rain-free day.
Continuity mistake: In the scene where XXXX and Lucky are in the park waiting in order to assassinate Dragan - after Dragan shoots Lucky and is talking to XXXX on the phone, the bag that Lucky was resting his gun on changes position between shots.