The house of writer and director Sir John Boorman was robbed by the real-life Martin Cahill. Among other things, he stole a gold record that Boorman had on the wall (an award for the "Dueling Banjos" theme from Amargo Pesadelo (1972)), which inspired Boorman to include that scene in the movie.
When the film was shown in theaters, it was in black-and-white, but when it aired on American cable television networks, it was shown in color.
Although, as the film reflects, Martin Cahill would wear a balaclava or cover his face with his hands at public appearances when he would be photographed by the press, he would also pull back his outer clothes to reveal Batman T-shirts (or Mickey-Mouse-branded underwear).
Well known Irish director and writer Jim Sheridan has a small part in the movie as an anti-drug campaigner. He is the one challenging Adrian Dunbar's character.
The film portrays 'The General' Martin Cahill as a loveable rogue. In actuality, he was a violent criminal who shot and tortured anyone that crossed him. He was feared by the middle and upper classes but admired by the working class people.