Trivia: In the scene where Alice finds Bill's body hanging on the back of the door to the generator room, the producers purposely did not tell Adrianne King what they were going to do to the body nor did they let her see the body beforehand. When she saw the body during filming it was for the first time. The scream she produced was genuine as it scared her badly. Needless to say, that entire scene was shot in one take.
Trivia: A sequel to The Long Good Friday was written by screenwriter Barry Keeffe. Entitled The Black Easter Monday, the action starts immediately after that of The Long Good Friday when the car carrying Shand is stopped by police. Both Shand and the IRA gunman (played by Pierce Brosnan in one of his first film roles) bluff their way out of it and walk away, allowing Shand to escape. The screenplay was universally acclaimed but by the time it got through development hell Brosnan, Bob Hoskins and Helen Mirren had all become big stars. They could not commit to the project and their salary demands could not be accommodated anyway. The film was never made.
Trivia: Writer-Director John Carpenter appears in the film as Bennett, Father Malone's assistant, at the beginning of the movie.