The Lisbon Traviata, King's Head Theatre, London

Jonathan Miller, whose nemesis is what he calls the DOOQ (Disgusting Old Opera Queen), had better steer clear of the King's Head while The Lisbon Traviata is on, but others will find much to amuse them in this tragicomedy by Terence McNally, the author of Master Class. Traviata's two moods, however, are split between its acts, which seem less like the halves of one play than a pair of pieces that sit together a lot less comfortably than Cav'n'Pag.

Stephen Henry's production opens with Stephen (Marcus D'Amico) visiting the New York apartment of the middle-aged Mendy (David Bamber), a royal DOOQ if ever there was one. In what looks like a set from a cut-price Tosca, Mendy pulls out record after record, both to entertain and to get one-up on his guest, while Stephen's lover spends the night with another man: "We're going through a phase." (The play was written in 1985; this is its British premiere. A few of its jokes are dated, but still funny. I laughed at Mendy's saying, when Stephen recalls a friend's monologue on his dinner with Susan Sontag, "Thank God they didn't make a movie out of that," though I didn't, at the time, pick up the allusion to My Dinner With Andre.)

Mendy is a hyperactive, obsessive Callas-lover, who calls his goddess "Maria" and objects when Stephen uses her last name. "It makes her sound far away." Mendy asks Stephen, "Why can't I find someone to love?" but the reason is obvious - this opera queen inhabits a kingdom where everyone must follow his laws, and where the response to anyone who doesn't love Callas is: "Off with his head!" Mendy is badly thrown when Stephen not only tells him about an exquisite Callas performance of which he was unaware, but says that he has a record of this rarity at home. Flapping and flouncing for all he's worth, Bamber makes a hilarious, if somewhat stereotypical, Mendy, especially when turning the flamethrower of his disdain onto people who don't know and don't care. An attempt to get a telephone number from Information (the New York name for directory enquiries) ends with his telling the operator witheringly: "Never was an organisation less aptly named."

The second half, in Stephen's apartment, trades bitchy wit for operatic grand passion, but it is overpowered by sentimentality and cliché. "Jesus!" exclaims Stephen to his lover, Michael, "what are you doing to me? What are we doing to each other?" It's not impossible for the smooth-talking, sensible Stephen of Act I to turn into the romantic volcano of Act II, but McNally doesn't make the transformation plausible, and it soon becomes risible.

Still, D'Amico, along with Tristan Gemmill as Michael and Matthew Thrift as the interloper, are all excellent. What grates on the ear, however, is a sloppiness in pronunciation (particularly of opera names) that further weakens the verisimilitude of this evening in the company of supposed perfectionists.

To 21 December (020-7226 1916)