In 1980s Belfast, a petty criminal (Jim Sturgess) lives a double life as a volunteer for the IRA while working undercover as an informer for a Special Branch officer (Ben Kingsley).

Inspired by Martin McGartland’s autobiography, this is an invigorating thriller with a persuasive script and brilliantly staged, nerve-jangling action sequences.

For more than four years, until his betrayal and subsequent discovery in 1991, McGartland estimates that he saved the lives of 50 men.

Giving credible, naturalistic performances, classy stars Sturgess and Kingsley are spot on, doing the story full justice.