The Old Masters, Comedy Theatre, London

With the strangulated upper-class English drawl that is his trademark, Edward Fox will not be everybody's idea of a Bostonian of Lithuanian-Jewish extraction. He last appeared in the West End playing Harold Macmillan, for God's sake.

With the strangulated upper-class English drawl that is his trademark, Edward Fox will not be everybody's idea of a Bostonian of Lithuanian-Jewish extraction. He last appeared in the West End playing Harold Macmillan, for God's sake.

In Simon Gray's new play, The Old Masters, Fox, making magisterially few concessions to the character's provenance, is a bizarre casting as Bernard Berenson, the great American 20th-century authority on Italian Renaissance art. But it's remarkable how robustly the piece survives this miscalculation, and the crude over-acting of Harold Pinter's surprisingly unsubtle production.

Gray's thought-provoking and beautifully constructed play trains its attention on the potentially corrupt relationship between art expert and art dealer, examining the human cost, for the scholar, of helping to determine the commercial value of pictures that transcend the market's idea of worth. The setting is "I Tatti", an idyllic villa outside Florence where Berenson, rich on the proceeds of his sideline in authentication, lives with his spouse (the superb Barbara Jefford) and his younger mistress (Sally Dexter). It's 1937 and ripples of anxiety are disturbing the Tuscan serenity. War looms and Mussolini's Italy is not the ideal home for a Jewish alien. Berenson's wife is terminally ill, there are money problems, and the scholar is in dispute with Joseph Duveen, the egregious art dealer with whom he has had a long and lucrative association.

The larger-than-life, but dying, Duveen (a game but not entirely convincing Peter Bowles) arrives with a proposition. He offers Berenson a complete partnership in his business. The strings? Keeping his mouth shut. Because the dealer wants to make a sale to an American millionaire, Berenson has to agree not to publish his reasons for believing that a painting, The Adoration of the Shepherds, is not by Giorgione (whose pictures have scarcity value because he died young) but by his more prolific, hence less profitable, pupil Titian.

Knowing a painting by heart is, we come to see, the most profound way of owning it. The play is wonderfully alive both to that and to the distorting compromises of connoisseurship. Like the pictures he judges, an authenticator has a market value. It's a vicious circle. You can't afford to give too many paintings the benefit of the doubt for profit, or you may lose the creditability that makes you valuable to dealers in the first place. That's Berenson's predicament. Gray arrestingly leaves open his precise motive for making a principled stand against Duveen and he's wryly alert to the snobberies of the art world.

It's a pity that the production feels forced and untrusting of the audience's intelligence, for this play about the dubieties of authentication is an indubitably authentic case of vintage Gray.