Theatre: BOOM BANG-A-BANG Bush, London

After the tawdry debacle of Eurovision (the gay musical that scored nul points in all categories) the idea of using the world's naffest of songfests as the context for another homosexual comedy might have seemed about as propitious a ploy as, ooh, building a pleasure cruiser and christening it the Titanic, or deciding to set a new soap opera in Spain.

Jonathan Harvey's Boom Bang-a-Bang at The Bush serenely soars over such superstitions. I have to admit that the news that his latest play was going to be set at a Kentish Town Eurovision Night party chez the kind of gay buffs who make a point of knowing their "Ding Dang Dong" from their "Ding-a-Dong" filled me with foreboding for a different reason. Harvey, still in his twenties, has just about the most natural ear for authentic- sounding comic dialogue of anyone of his generation. But with his two previous hits, you sometimes felt that the buckets of Scouse charm and the slightly coercive party atmosphere were failing to conceal an uncertainty about the issues raised (particularly in the attempted rape scene in Babies). Boom Bang-a-Bang sounded as though it would scarcely discourage these evasive tendencies.

Instead, it marks a marvellous leap forward in Harvey's art. It's a delight, but a delight with real bite. At one point, a charcter emerges from a long session on the loo bearing a copy of My Night With Reg. An in-jokey touch, but from the evidence of Boom Bang-a-Bang, you might suspect that Harvey also keeps a well-thumbed edition of Abigail's Party in his bathroom. Indeed, resentful, treacherous Steph (Gary Love), all officious false concern and snide confidentiality, seems to have dedicated his life to a round-the-clock impersonation of Alison Steadman's immortal Beverley from that play.

The Kentish Town party is significant for its absentees. Since their last Eurovision thrash, the lover of the host, Lee (Chris Hargreaves) has died. Of a brain tumour, not AIDS as it happens, although it seems that many of the couple's gay friends, who have decamped to an alternative party this year, think that diagnosis a hypocritical cover-up. Hence, to Steph's waspish annoyance, the undue number of straight guests at Lee's do.

No, make that 'straight' guests, for as the evening wears on, television sets blow up and conventional sexual categories are blown apart.

Director Kathy Burke and a brilliant cast do handsome justice to a play that combines farcical hilarity (such as the moment when Francis Lee's wonderful Roy drops some ecstasy and becomes disastrously indiscreet as he loses all his previous knotted anxieties), gimlet-eyed observation of gay sub-culture (watch out in the Oxford Street Top Shop), and a plot that intelligently exposes the limitations of gender stereotypes and sexual pigeon-holing - how it can make seemingly perfect sense, say, for Jane Hazlegrove's aggrieved Wendy to tell her female lover: "You're a man. You do the same sort of things men do. Fuck women up." Or for straight Nick (Karl Draper) to feel wistfully that he would be better off in a relationship with Lee than with his partner. The play rattles open compartments without making the simplistic suggestion that everybody is "really" gay. Still ridiculously young and talented, Jonathan Harvey is now becoming seriously good.

n To 19 Aug (Booking: 0181-743 2223)