Imagine Billy Elliot doing smack. Ten-year-old Paul supports West Ham football club and his mum (a typically courageous performance from Molly Parker), a heroin addict since Paul's dad died. The lad himself is only vaguely aware of what a junkie might be, but he's curious to find out, and living in this impoverished, unsentimental corner of East London it's not long before he does. MacKinnon's tough, bleak film, written by Alison Hume, feels honest and sincere, even if it doesn't always ring quite true. It's buoyed no end by young Harry Eden, anguish and resolution inscribed on his face. Look too for another remarkable turn from rising star Keira Knightley.