Lucky Seven, Hampstead Theatre, London

One has to be suspicious of any new play that contains old jokes, such as "What's a Grecian urn?" (About two drachmas a day, if you must know.) But Alexis Zegerman's debut comedy overcomes these lapses to make some sharp points about television documentaries in general and Michael Apted's ongoing Seven Up! series in particular.

Her three characters come together once every seven years to be filmed for posterity. They don't much like doing this, nor do they even much like each other. But they seem to have no choice in the matter, and in unhappy, depressive Tom's case, the show has become an albatross round his neck. He wants the unseen director to make a film of his life in Hollywood, preferably with Mel Gibson in the leading role.

You only have to look at Jonny Weir's sad and crumpled middle-class Tom to see how ludicrous that film might be. He has been to Cambridge to read English and is now an archivist. Susannah Harker's blonde, upper-class Catherine – and Catherine Deneuve would not be inappropriate casting, perhaps – has breezed through married life only to run into a brick wall of grief. And David Kennedy's working-class rude boy, Alan, manufactures women's knickers and lives – is this another bad joke? – in Bushey.

The play takes too long zipping between the generations – we mostly see the trio at the ages of 21 and 49 – to establish any meaningful theatrical overlap between the filmed interviews and real-life interaction. And the pile-up of information leaves no time for drama, until a rather desperately contrived sex scene towards the end.

But Zegerman and her director, Anthony Clark, do make some suggestive comments on the public nature of private lives these days in both reality television and the realms of unearned celebrity. And the performances are cunningly pitched at moments of crisis that flash up whenever they get together, and the ageing process becomes all part of the package.

The television director, like Godot, never turns up. You can hardly blame him: Catherine is about to sue him for causing her son's death, and Tom wants his life back. And Alan's wife has run off with the accountant, though that doesn't fully explain why he's stashing egg mayonnaise sarnies in his inside pocket. I guess we're just witnessing everyday ordinary existence.

To 22 November (020-7722 9301, www.hampsteadtheatre.com)