Yellow Face, National Theatre

Yellow Face comes into the Shed a year after it was first greeted enthusiastically at the newly-opened Park Theatre. Its category was generally agreed to be "mockumentary". Fair enough as the author David Henry Hwang appears as a character in his own play, a mixture of autobiography and fiction.

Hwang was inspired to tackle the subject - the lack of opportunity for East Asians in American theatre - when Jonathan Pryce was cast as the Engineer, complete with taped up eyes, in Miss Saigon, adopting "yellow face" in the tradition of "black face" minstrels. Hwang led the protests against Pryce's casting and out of that has spun the play.

The documentary form isn't all that is mocked. The comic plot hinges on the fact that it is against American Equity rules to enquire in so many words as to an actor's ethnicity. Hwang enjoys poking fun at this political correctness: a white actor is mistakenly cast as Asian in a play - Face Value - by none other than arch-protester David Henry Hwang himself. Marcus G. Dahlman, who can claim Jewish and Siberian ancestry - Siberia being helpfully just north of China - becomes, as Marcus Gee, a Chinese-American success in the role of the King of Siam in The King and I.  Hwang is mortified and does his best to undermine Gee's success. He, meanwhile, warms to his role and becomes a leading advocate for the Chinese - now "his" - community. Underlying this, of course, is the fact that people in multicultural societies do not necessarily wear their ethnicity obviously on their faces.

Hwang is clever enough to mock himself too. What could be more vain that making yourself a lead character? Hwang is quick to say so before anyone else. There is even a line to the effect that no-one could take seriously a character in a play given the playwright's name. This is, nevertheless, self-regarding stuff, but DHH gets away with it because - apart from sending himself up - he makes a serious stab at tackling some of the complexities behind the slick comedy. How big a part does ethnicity play in a person's notion of identity? If it is true that most human beings feel a need to "belong" in a community, how big a part does shared background or similar appearance play? Can simply wanting to belong be sufficient reason to be accepted? Where exactly is "home"?

The plot takes a darker turn when China begins to be seen as America's next enemy and Chinese-Americans are accused of helping foreigners to influence elections. Hwang's father, a banker, always dreamed of being an American, looking up to screen heroes like Jimmy Stewart. He is, ultimately, deprived of that dream by American paranoia.

The actors - slipping into numerous roles, Brit and American - jump up from among the audience seated on all four sides of an under-lit square stage. Alex Sims directs with the necessary zip but without compromising the clarity of a complicated story told by dozens of voices. The cast are excellent, with veteran David Yip especially memorable as Hwang's father and Kevin Shen and Ben Starr (pictured above with Gemma Chan as Leah) playing DHH and Marcus respectively with terrific humour and attack.

Special Relationship Productions was set up to "give greater exposure to under-represented groups in theatre". More power to them if they continue to present plays as engaging and provoking as Yellow Face.

• Yellow Face at National Theatre until 24 May