THEATRE REVIEW / Chaos theories: Rhoda Koenig on the West End transfer of Tom Stoppard's 'exhaustingly brilliant' Arcadia

You can stir the jam into the pudding, observes Thomasina Coverly, but you can't stir it out again. This teenage mathematical genius of the Regency is demonstrating the flaw in Newtonian physics, but her metaphor could also apply to the tom-cat among the pigeons or the bee in the academic bonnet, to name only two chaos-bearing elements in Tom Stoppard's play. A romantic, historical and mathematical mystery, Arcadia shows how intellectual and erotic energy, as well as crude ambition, will generate brilliance and mischief, even after their generators are exhausted or dead.

For the West End transfer of the National Theatre's success of last year, Trevor Nunn has assembled a sturdy cast. In the contemporary scenes of this sometimes exhaustingly brilliant play, Roger Allam's portrayal of the swaggering Byron scholar Bernard Nightingale gives us a caricature to match any Regency beau in extravagant self-praise and offhand sexual invitation. This media-wise don plugs his theories with feet planted firmly apart, knees bent, and forearms raised, as if about to launch into a chorus of 'Mammy'. He switches on a look of pleading- doggie wistfulness when trying to soften up a competitor, and sort of lopes on the spot. But, though entertaining, he is out of kilter with such characters as Rachel Fielding's note- perfect Chloe, the kind of pretty girl - as familiar in conventional West End comedies as in real-life country- house parties - whose terribly nice intentions are matched with a tiny mind and a cute little heart.

As Hannah Jarvis, a more sober academic who is disdainful of Bernard's wishful thinking, Joanne Pearce is, despite some strident perkiness, far more believable. But she might have been even colder and drier at first, with some genuine wistfulness to soften this unfeminine woman as she realises that her research into the Romantic period is leading her down a crooked path to an actual romance, one in which a dead virgin inspires more passion than the most flaming Byronic conquest. The vulnerability in the modern scenes is supplied by the mathematician Valentine, whose pet tortoise symbolises his slow start but triumphant finish in the intellectual race. At first dismissing Thomasina's notes of her equations, Valentine pushes her premises to their conclusion, not only earning Hannah's respect but emerging from the shell of timidity which Charles Simpson's sensitive performance renders touchingly disturbing as well as comic.

Valentine's tenderness recalls that of Septimus, Thomasina's tutor in 1809, whose extra-curricular attentions embrace the lady of the house as well as a flamboyant guest. Edward Atterton, starting off a bit like a Regency public-address system, soon relaxes into the part of the overly articulate young man who pays tribute to his growing love for his pupil with silence. Consoling his charge as she weeps over the destruction of the library at Alexandria, he says: 'The procession is very long, life very short. We die on the march . . . Others pick up what we leave behind.' The last seems a frigid comfort, but, after we see the long-dead Thomasina's theories reborn, it little matters whose hand inscribed the work that lives. And Thomasina herself converts Septimus's point into a life-affirming proposition. Lucy Whybrow's charming prodigy, as ingenuously radiant over her discovery of kissing as of fractal geometry, cries, 'We must hurry if we're going to dance]'

What the production's strengths don't disguise, however, is that Stoppard's concept outdistances its execution: the philosophical, scientific, and emotional ingredients of the play often remain apart, like peas in a jelly, rather than swirling together like the pudding and the jam. The unremitting cleverness has neither the power of true wit nor of unexceptional remarks emerging, with pointed brilliance, from well-drawn characters. When Arcadia stops for breath, and feeling, it gives us something more than classy chatterers; but, on the whole, one feels the need of a few more shadows to balance all that brightness.

At the Haymarket Theatre Royal, London SW1 (071-930 8800)

(Photograph omitted)