The Chinese words on the package are the title of "The Departed", which is written by William Monahan as well. Infernal Affairs (the movie The Departed was based on) was incorrectly called "a Japanese film" during the 79th Academy Awards; Jordan emphasizes "he got it from Hong Kong" here.
The film differs significantly from Ken Bruen's novel in that the movie star that Mitchel beds is a sexagenarian, unlike the significantly younger Keira Knightley.
The screenplay for this film was featured in the 2008 Blacklist; a list of the "most liked" unmade scripts of the year.
On the Bluray disc, William Monahan stated the scene between Gant (Ray Winstone) and DI Bailey (Eddie Marsan) was shot at a specific point next to the River Thames because it was important to him. However, he did not reveal to anyone why. It appears to be the exact same spot that "Alex DeLarge" (Malcolm McDowell) is beaten by all the old winos and bums after his treatment in "A Clockwork Orange".
The book that Gant is reading in bed near the end of the film is the Penguin edition of "The Social Contract" by Rousseau.