Southwark Fair, National Theatre: Cottesloe London <!-- none onestar twostar threestar fourstar fivestar -->

A nonagenarian South African actress who was once in an episode of Catweazle; a one-handed American folk-grunge-rock singer-songwriter and her bisexual Irish film-biographer husband; a Hungarian-Canadian waiter and his New Labour boyfriend; a migrant Australian street-performer; and, at the centre, a gay thirtysomething IT technical support analyst for a property consultant behind Tate Modern.

All human life is here: or, then again, not. One of the frustrating aspects of Southwark Fair - and there are a few - is that Samuel Adamson seems to have been unable to decide whether to create a sweeping satirical portrait of contemporary metropolitan life or a comedy of gay manners. But he has such fun that it's hard to feel too cross about it.

The action begins in a coffee bar: here, Simon (Rory Kinnear), the technical support analyst, banters with his dotty elderly neighbour, May (lovely Margaret Tyzack) and a snipey barista, and worries about his lunch date: he has been rung up by the first man he ever had sex with, back when he was 14 and playing Puck in a summer-school production of A Midsummer Night's Dream. Simon has big expectations of this lunch, but they are confounded when it turns out that Patrick (Con O'Neill) was actually thinking of the boy who played Lysander. After a fractious lunch, Simon finds out he's been followed by Patrick's wife.

So far, the play meanders along, with some superbly funny jokes along the way - the awkward lunch, in particular, is a delicious concoction. The second half starts out as a recap, but from different perspectives: now we find out why Aurek the waiter was in such a mood, and see the effect that meeting Simon has on Patrick. The elaborateness of the structure seems superfluous, but it does allow Adamson to string together some of effective running jokes (one involves a boxing glove that once belonged to Marlon Brando, and the obscene uses to which it has been put).

All in all, Southwark Fair is a messy, self-indulgent piece, short on momentum, characters sketchily drawn, dialogue seesawing between brilliance and banality. But when it's good it's very, very good, and Nicholas Hytner's production smooths over a lot of the cracks. Giles Cadle's set, with its bold Patrick Caulfield outlines, neatly captures a vein of over-strenuous modernity.

To 10 June (020 7452 3000)