Gwyneth Paltrow proved that Sam Mendes' decision to cast another Hollywood star in a high profile role at the Donmar was fully justified when she led the cast in a tearful but happy curtain call to a standing ovation from the opening-night audience on May 15.

David Auburn's play revolves around the discovery of a brilliant, highly complicated mathematical "proof," one that explains and justifies a fundamental mathematical principle. Unlike Michael Frayn's Copenhagen, which went into some detail about the nuclear physics that was at the core of his play, Proof involves a lot of reference to mathematical genius without troubling the audience with any actual math.

Acting in a cast of four — veteran National Theatre actor Ronald Pickup played her brilliant but mad father, Richard Coyle (fresh from playing a gay theatre director in The York Realist) played his pupil and her boyfriend, and Sara Stewart (in a performance that nearly stole the show) played her sister — Miss Paltrow proved herself as a stage actress as well as a film star.

The action takes place on the porch of a family house, where Paltrow's character, Catherine, nurses her ailing father, Robert. The set revolves with each change of scene and the scenes themselves jump forward and backwards in time.

The audience reaction to the play's denouement — a mercifully happy ending — was suitably ecstatic for a Donmar first night, and the photographers who crowded around the theatre's tiny lobby were rewarded with more than the usual group of theatrical celebrities.

The reaction of London's drama critics may have been immaterial in that the play has been comfortably sold out for months, but the audience — and critics — approval have been a welcome bonus for Paltrow.

—By Paul Webb Theatrenow