Advertising posters showing a bloody hand sliding down a London Underground train window were banned from the Underground as being in bad taste, even though scenes had been filmed with permission in disused stations on the Underground. Producer Julie Baines found this "highly amusing" and "a bit ludicrous", noting that the film is "not based on real events - if it is, we are all in trouble." The ban was later removed, although not in time for the film's British opening.
The image of the bloody hand on a carriage window was allowed to be displayed in London Underground stations for the DVD release, unlike the poster for the theatrical release.
In the scene with Jimmy and Kate on one of the trains, there's a dead guy (the train driver) lying on the floor. If you look closely you see he has a moustache. It was actually added on later using CGI so he wasn't confused with the previously killed security supervisor.
The villain, Craig was named after the director Chris Smith's friend, Craig Fackrell who played a homeless guy by the cash machine in the film.
When they were filming Franka running through a tube train, the cameraman behind her ran straight into one of the posts on the train.
Titles that didn't make it: "Runt", "Cellar Dweller", "Horunder", "Here Kitty Kitty", "One Track Mind" and "Piccadilly Nightmare".
They bought six yellow dresses for Franka, each one had a varying degree of dirtiness because her dress got more grubby throughout the film.
Franka Potente dubbed her own voice in the German Version.