US And Them, Hampstead Theatre, London

We may find them a bore, but humourless people perform a valuable role in the world. They do the jobs that must be done, and that never would be done if left to the clever, the sceptical, and the detached. I do not know Jenny Topper, artistic director of the Hampstead Theatre, but it is clear, from the excruciating comedies she presents there, that she is one of these people.

Topper will soon be leaving this post, and leaving behind, as her monument, the immensely stylish new theatre that represents years of drudgery with planners and builders and lottery bureaucrats, But this elegant space, like its Portakabin predecessor, houses plays that are insufferably patronising, prissy and arch; plays that perch brightly, tightly smiling, far from human life.

One can't say that Tamsin Oglesby doesn't give fair warning. Her title - US and Them - is representative of the level of humour displayed in this play about two middle-aged couples - one English, with a daughter, the other American, with a son - who become friends, then part. The first scene is a preview of the penultimate one, in which Ed, the American husband, tells Charlotte and Martin that, while they are "great guys", the "association" has started to "impact badly" on him and his wife, and "I'm afraid we have come to the conclusion, albeit with regret, that we don't want to be your friends any more".

The play then goes back to the beginning of the friendship, when Charlotte and Martin, newly arrived in New York, meet Ed and Lori in a highly-contrived restaurant encounter. Charlotte says that her coat has been damaged, and Ed steps in, insisting she be compensated. Then the flaky Charlotte realises that her coat is actually unharmed, but the two couples,deciding that the truth would be embarrassing after the fuss they have made, leave without saying anything. Thus begins a friendship whose keynotes are money (Martin and Charlotte are middle class, Ed and Lori rich) and misapprehension. Ed helps Martin in a business project that founders; Lori makes an assumption about Charlotte which the latter does not correct.

That is what the play portrays, but what, in God's name, is it about? With its precious dialogue and its single- attribute characters (Ed is pompous, Lori well-meaning, Charlotte dizzy and Martin nice), US and Them succeeds neither as a play of ideas nor as entertainment. It has the brittleness of high comedy without any of the wit. Jennie Darnell's direction is characterised only by would-be chic sterility. Harriet Walter is one of my favourites, but as Lori she re-uses the bizarre and irritating accent she adopted for The Royal Family, one that sounds like a small girl ineptly pretending to be Katharine Hepburn, and at times resorts to pleading for a laugh. Hugh Bonneville as Martin turns in a relaxing, beautifully-timed light comic performance, perhaps because his character is the least strictly defined, and Jonah Y Lotan, as the American boy, has a pleasing quality of repose.

When Siobhan Redmond, as the predictably-lefty Charlotte, throws friendship to the winds and starts shrieking about America's illiterate and murderous president, quite a few of the first-night patrons sharply drew in their breath at this daring, then broke out in murmurings of approval and a sprinkling of applause. With plays like this, the Hampstead Theatre may know its audience, but one hopes it will soon find a better quality of both.

To 28 June (020-7722-9301)