Howard Brenton's majestically simple, modest and beautifully presented new play is an art gallery installation based on a recently published book by journalist Barnaby Martin about the 81 days of detention endured by the Chinese artist Ai Weiwei.

A celebrity tweeter with a "hooligan" tendency and a suspect reputation for big sales in a decadent Western market, Weiwei was arrested on trumped up charges of tax evasion, even though the authorities have come to realise that his cause is only reinforced by their actions; he currently lives at home in Beijing in what has been described as a state of suspended animation.

In becoming his own art work, he's now prompted this vividly Kafkaesque account (which is live-streamed free tomorrow evening on multiple platforms, including Whatsonstage.com) of incarceration, enforced silence, supervised loo visits - Weiwei takes a wee-wee - and aggressive interrogation.

But in the second act, Brenton shifts the emphasis to show how captors are prisoners, too. In one hilarious scene, the guards and Weiwei march up and down in a confined space articulating stiffly between their teeth like ventriloquists so that the CCTV doesn't show they are talking.

That space is the interior of a huge crate that bursts open in a large gallery where a dozen visitors - who double as the stage-management team - are overseeing the spectacle and taking photographs. Benedict Wong is an imposing, bear-like presence as the genial Weiwei, turning one interrogation scene into a detailed discussion of the best recipe for noodles.

And he's deftly supported by a well-drilled cast of officials and soldiers, seated between scenes at the side on chairs along with the "extras," including Junix Inocian, Richard Rees, Andrew Koji, Christopher Goh, Andrew Leung and David K S Tse.

The show, which is patiently and precisely directed by James Macdonald, with a superb design by Ashley Martin Davis that uses the full area of the Hampstead stage, and the scene dock, works as an obvious metaphor of the state's paranoia about any kind of engaged artistic expression. But it also becomes a debate about the dynamic in art between the creative spirit and the general public.

The officials eventually stumble on Weiwei's Dadaist tendencies, relieved at last to identify their prey in a wider "corrupt" cultural context; as one of them is wearing a Ryan Giggs Manchester United shirt, any further ironic comment is unnecessary.

Two suited high-ups are seen in the "correct" cultural setting of scrolled down boughs of flowers and canned Mozart emanating from tree trunks - "Get him to go back to leaves and pagodas," is their command - an image that suggests a fear of individualism, in art and life, that is anathema even in the aftermath of Mao's revolution.

Wong delivers a powerful argument for freedom of speech before performing a re-enactment of one of Weiwei's most famous desecrations on a bare stage, a brilliant conclusion to a piece of theatre that is both a public service and an absorbing, imaginative response.

- Michael Coveney

Whatsonstage.com will be co-hosting the live stream of #aiww: The Arrest of Ai Weiwei tomorrow (19 April) - tune in from 7.25pm