Presumably, when this treatment of a tricky subject in recent Northern Irish history - what makes someone turn informer - was put into production, the Troubles were gradually receding into the past as the peace dividend took hold. Now, though, with the re-emergence of paramilitaries, Fifty Dead Men Walking stands as an all-too-horrible reminder of what everyone thought had been left behind.
It's adapted from a memoir by Martin McGartland, about his time as a Provisional IRA operator in the late 1980s feeding information to Special Branch, before he was unmasked in 1991. (The title refers to his estimation of the number of lives he saved.) It's also proved bit of a minefield for the film-makers: McGartland has protested that his role in IRA brutalities is misrepresented, and ill-advised comments by Rose McGowan (who plays a frankly preposterous ultra-sultry "IRA intelligence officer") haven't helped.
Be that as it may, producer-director Kari Skogland has put together an effective, if cinematically unambitious, enterprise, emphasising the suspense-thriller elements that come naturally to the story of a man terrified of being found out at every turn. Inevitably, this comes at the expense of sophistication of political and historical insight; like trying to ride two horses at the same time, Skogland is having to address an audience who may know nothing about the conflict, and those who know it inside out. Her best weapon is lead actor Jim Sturgess, who is terrific: relaxed and note-perfect as the opaque McGartland. Ben Kingsley, playing his Special Branch handler, can't stop himself lapsing into the bizarre Dick Emery mode he's dabbled with since Sexy Beast.