Directed By Gillies McKinnon. Starring Molly Parker, Harry Eden, David Wenham, Keira Knightley.

The damaged streets of London's East End are the perfectly bleak setting for this powerful, wonderfully acted drama of urban decay and drug addiction. From a director best known on this side of the water for his Oirish melodramas, 'Trojan Eddie' and 'The Playboys', 'Pure' is firmly in the tradition of British urban realism as pioneered by Ken Loach and Mike Leigh.

Ten year-old Paul is the film's protagonist, its eyes, ears, brain and heart. Paul’s character is a modern film cliché - the wise, caring youth who often knows better than the child-like and venal adults that surround him.

The narrative of 'Pure' entirely depends on Paul, requiring an extraordinary performance from Harry Eden, who is a revelation delivering the best juvenile acting I have ever seen: naturalistic, charming and deeply sympathetic.

Molly Parker is also excellent as Mel, Paul’s heroin-addicted mother who, predictably, endures desperate privations and does dreadful things while in thrall to her habit. David Wenham (last seen with an iron helmet over flowing locks as Eomer in 'The Two Towers') is convincing as the sleazy, conflicted Lenny, Mel‘s dealer and lover. Despite being Canadian and Australian respectively, the two are perfectly convincing as Eastenders.

The film's weak spots are its occasional implausibilities. Louise, the teenage waitress (Keira Knightley) has the exquisite face of a pampered RADA graduate, and displays an unlikely sexual interest in Paul (he is ten years old for God's sake).

This story of life at the wrong end of London’s social scale may not be hugely original, but it is utterly believable and involving. The cinematography is unshowy, making the best use of the grimy, exotic markets and strangely ragged textures of the streets around West Ham. The druggy scenes are restrained and well-realised, while Nitin Sawhney's resonant soundtrack is suitably multi-ethnic. Unlike so many of its characters, Pure's emotional grip never weakens.

Luke McManus