Directed by Josh Schwartz. Starring Victoria Justice, Jane Levy, Thomas McDonell, Chelsea Handler, Johnny Knoxville, Abby Elliott 12A cert, general release, 90 min

THE LIFE OF the artist Ai Weiwei has been characterised by constant revolution. The son of Communist poet Ai Quig, the younger Ai witnessed his father fall from Party favour during the Cultural Revolution, when the family was sent for reeducation in the remote Xinjiang region on the Pakistan border.

In common with directors Chen Kaige and Zhang Yimou, Ai graduated with Beijing Academy’s Fifth Generation of film-makers. In 1981 he relocated to New York, where he found contemporaries among the No Wave subcultures.

Ai’s work is duly defined by protest. He flips Tiananmen Square the bird in a series of iconic photographs; he spray-paints and smashes ancient Chinese artifacts; he tweets every day about the state of the nation. In China and in the art world, Wi is a rock star, replete with flunkies, apprentices, a fan-base and a young son by a mistress. (This film keeps us waiting to discover what his wife, fellow artist Lu Qing, might make of that particular domestic complication). His studio is the PRC’s answer to Warhol’s factory, a place where the master’s ideas are realised by craftsmen and sculptresses, who liken themselves to assassins.

But Ai’s status, as documentarian Alison Klayman soon discovers, may not be enough to protect him from the authorities he seeks to criticise.

Klayman’s fascinating, crusading picture is a happy accident. The American journalist was shooting Ai’s campaign to collect all the names of children killed in shoddily built schools during the 2008 Sichuan earthquake just as the project sparked the interest of government agencies.

Friends and family repeatedly acknowledge that Ai is a hooligan and instigator; Ai repeatedly owns that if he does nothing, nothing will change. In the run-up to major exhibits in Munich and London, there’s a palpable sense that things are coming to a head.

This essential, finely honed biographical portrait is jollied along by all the ironies and complexities of modern China. Time and again we see dissidents arrested and sentenced for Orwellian-sounding crimes, but their very existence trumpets change. As Ai’s plight, onscreen at least, comes to a dramatic, unexpected close, there’s an equally unexpected sense of optimism. TARA BRADY