The Old Country, Trafalgar Studios, London <!-- none onestar twostar threestar fourstar fivestar -->

First impressions prove to be deceptive in The Old Country, Alan Bennett's beautifully written 1977 play, patchily revived now by Stephen Unwin and English Touring Theatre. The very English scene that greets the audience - the book-cluttered veranda of a country residence; Elgar wafting from a gramophone; urbane, literary chat; the owner in a Garrick Club tie - is gradually exposed as a fake.

This is, in fact, a dacha in the Soviet Union where Hilary, a Foreign Office spy who defected 13 years earlier, and his long-suffering wife, Bron, live in a kind of time-capsule of the England he grew up in and betrayed. The couple are awaiting a visit from Hilary's sister, Veronica, and Duff, her newly knighted and absurdly well-connected husband who is under instructions to persuade Hilary to return to England as part of an exchange deal with the Russians.

As in his play about Guy Burgess, the exile of an upper-class traitor provides Bennett with an excellent vantage point from which to examine Englishness. Irony is shown to be both our national blessing and our curse. It's a way of being in two minds and is a form of disguise: "Joking but not joking. Caring but not caring. Serious but not serious." And treachery, we gather, is irony in action - a very practical way of hating what you love.

The Old Country is itself a wonderfully knowing exercise in ambivalence. Take the terms in which Duff, a pompous pillar of the Establishment, splendidly played here by Simon Williams, explains to Hilary why he can't expect all to be forgiven on his return home: "The fact remains, there were deaths, disappearances. People... died. Some of them first class."

That demonstrates a snobbery, though, that Hilary shares. Revealingly, he is quite prepared to countenance the double standards whereby he is repatriated, thanks to fancy connections, and desperate Eric, a young lower-class draughtsman (attractively played by Tim Delap), is left behind.

If Hilary were to be ideologically consistent, he would be glad to hear that England has changed. Temperamentally, though, he wants it to be as fixed as the version he has preserved in amber here with his endless parodies of John Buchan and Times obituaries. "It must stay the same or there is no point in having come away," he declares, conscious of the paradox.

Timothy West is not well cast as Hilary in this demanding role. There's something too downright straightforward about him. Hilary needs to be a trickier customer, elusive behind smokescreens of defensive irony. As his wife, Jean Marsh offers a touching study of a woman who could have been a boon to the community in Blighty and has instead withered in exile and grown tart. And Susan Tracy is delicious as Hilary's droll, worldly sister.

Booking to 6 May (0870 060 6632)