Writer/director Jacques Audiard’s Oscar-nominated French jail house drama A Prophet (Un prophète) is a long, deliberating and ultimately debilitating two-and-a-half hour journey – but by god, it packs a punch.

A 19-year-old Arab man named Malik el Djebena (Tahar Rahim) is sentenced to six years in jail, where he is selected for special duties by criminal kingpin Cesar Luciani (Niels Arestrup). El Djebena is quickly confronted with a grim choice: kill a fellow inmate or be killed. He goes ahead with a bloody murder, which kick-starts his ascension in the slammer’s criminal hierarchy and, of course, further charters his dramatic declination into drug deals, turf wars and savage prison yard politics.

Tahar Rahim is outstanding in the pivotal role: his performance is a lit fuse of powerful, understated and finely nuanced acting delivered with a cool, calculating menace. Devoid of moral judgements, A Prophet’s screenplay follows el Djebena’s plight with a clinical, hard-hearted weariness. Audiard conjures an airtight sense of realism and plunges the viewer into a cold and remorseless world, made intensely personal by a small number of vividly rendered personalities – men whose browbeaten, hangdog expressions will linger long in the memory.