Guy Pearce was at one point set to play Mac.
Screenwriter and author of the original novel Tom Bradby appears as himself in news footage early in the movie, although he is credited on screen as Patrick Clacy. Bradby is a news reporter for ITN who was stationed in Northern Ireland during the period in which the film is set.
Rebecca Hall was the first choice to play Colette.
Clive Owen originally turned down the part of Mac due to scheduling conflicts.