The Chinese artist Ai Weiwei keeps cats in his studio. These cats prowl over his desks, pawing at his models and maquettes; one of them has even learnt how to open a door, though - as Ai himself observes - unlike a human visitor, he doesn't much care to close it behind him. Alison Klayman, the documentarist behind the very fine Ai Weiwei: Never Sorry, puts this revelation upfront, perhaps to suggest how a spirit of wily, feline intelligence (and intransigence) permeates the artist's work. For newcomers to Ai's work, this is the individual commissioned to design the Bird's Nest Stadium for the Beijing Olympics, only to then be photographed giving the completed edifice the finger - and widely reported to have turned his back on the Games themselves, denouncing them as a PR exercise for a corrupt, oppressive regime.
This bearded, bear-like man works across several disciplines, and proves full of contradictions, which maybe explains his reluctance to toe the Party line. While he seeks to put an end to certain Chinese cultural traditions - hence his photographic self-portraits, featuring the artist shattering Han dynasty vases, or his respraying of other urns with the Coca-Cola logo - Ai is very much the son of his father Ai Qing, a poet exiled and persecuted during the Cultural Revolution. If you like, he's chosen to perpetuate his family's own long tradition of dissent, however troubling, even painful, a burden that might be for one man to carry.
What distinguishes Ai's work is that his aren't the empty gestures of provocation made by certain Western contemporary artists. Though it was with the Bird's Nest that Ai first turned heads internationally, he first began to establish himself as a dissenting voice in the wake of the 2008 Sichuan earthquake, when he and his team of volunteers visited villages affected by the disaster and tallied up the names of the five thousand children killed when jerry-built Government schools collapsed on them; this data was later published, against the Government's wishes. (The photos of the dead schoolchildren's backpacks - which formed the basis for the artist's 2009 exhibition in Munich - are unbearably moving, doubly so when you realise that these were the families' only children, as dictated by Government policy, bearing hopes and expectations that were literally crushed by the State.)
It's true that, like all modern artists, Ai has grasped that it pays to put himself out there - eating at street restaurants (where he's frequently interrupted by his fans), Tweeting whenever possible - and Never Sorry is, on one level, a continuation of this process. But the reward here is greater than money: it's liberty. The more public Ai is, the less likely he is to be disappeared by the authorities. Klayman's film addresses the criticism that Ai is now more brand than artist: we see him opening shows around the world, and - Hirst-like - employing a small army of his own to help assemble the pieces he displays. Yet this looks more like a necessary survival strategy than a desperate bid for celebrity: it's his way of announcing that, as with Coca-Cola or Starbucks, he isn't going away any time soon.
That element of documentation so essential to his art feels more utilitarian than anything else: numbering and naming the earthquake victims, for example, is something the Government should be doing, surely. As for that self-documentation, it's of a variety more commonly found in female artists such as Tracey Emin or Lena Dunham, born of a need to make their presence felt, their voices heard, in hostile patriarchal environments. However conceptual it gets, Ai's work is grounded in lived experience; here's someone who really has suffered for his art. The cameras were there when, in 2009, he was beaten by the police for attending the trial of a friend, and subsequently suffered a brain haemorrhage; scuffles and tussles with undercover officers look to be an everyday occurrence, and while Ai has the physical bulk to handle such daily battles, we sense the draining emotional toll they must take.
His themes of transparency and responsibility come across loud and clear - he's only too willing to answer questions from a reporter about the child he fathered outside his current marriage - and his personality leaps off the screen: this is a warm, mischievous, funny individual (his gnomic Tweets are works of art in themselves), who's generated immense loyalty in both his acolytes (who refer to him as "teacher") and the wider public (who sent money to help him pay off the tax bill the authorities stuck him with). Klayman catches his comic reluctance to bring on his mother, who will surely, he says, complain about her son's eating habits and burst into tears - she does both - but also his offer of a seat to a female officer obliged to stand throughout one of the long transcription processes he's legally required to go through. The porcelain sunflower seeds, stymied by UK health-and-safety law upon their appearance at Tate Modern in 2010, arrive late in the film, by way of a million hand-carved full stops, but this is a hugely engaging, endearing and well-rounded profile of one of the modern art world's foremost communicators, making a courageous bid to throw all the doors open - and keep them open.
Ai Weiwei: Never Sorry opens in selected cinemas from Friday.