Zoe Wanamaker and Simon Russell Beale make a far bigger and better splash in Nicholas Hytner's alluring production of Much Ado About Nothing than I dared hope. As Shakespeare's young antagonists, Beatrice and Benedick, whose witty war of words masks mutual attraction and concludes in an armistice dictated by love, they are from conventional casting.

Benedick, a soldier-lord and Beatrice, the Governor of Messina's browbeaten niece, are elegant and sophisticated, young and aristocratic. Despite their high talents neither of these actors is a natural recipient of these adjectives. Yet John Gielgud and Peggy Ashcroft famously led the way in the Fifties, revealing how these roles could be moulded to suit middle-aged performers or an unheterosexual actor of Gielgud's make-up.

Hytner's production bursts into exuberant, situation comedy. It does not, though, boast a concept or concern itself with the psychological make-up of the soldiers who unite the romantic and dramatic plotlines. Designer Vicki Mortimer locates the play in a strange no-man's land. The costumes mix 16th and 19th century styles.

Attractive, white-washed Sicilian houses are foregrounded by a revolving stage on which are placed hideous, wooden, vertically slatted screens and a paved walkway - all fresh from Heal's, I guess. A small swimming pool, Mediterranean sunlight, sounds of dogs, chattering townsfolk, dawn chorus birds, music and human singers complete the vivid Italian picture.

Wanamaker's dazzling, fiftysomething Beatrice appears a vinegary, cynical outsider in her own family.

She greets Russell Beale's comically swaggering Benedick, sporting a pointed beard and pronounced air of condescension, with tart disdain. The key to this vulnerable Beatrice is her sad sense of being a middle-aged romantic on the shelf.

She gives herself away when in wistful melancholia she refers to Benedick winning her heart "with false dice". Once spurned and now in payback time, her wit at his expense displays a serious, cutting edge. The broadly played discovery scenes, when both eavesdrop in the garden and discover each is secretly in love with the other, rise to two terrific, watery climaxes.

Russell Beale, almost caught in the listening act, slips headlong into the pool and rises all wide-eyed, with the comic-pathetic astonishment of a man who cannot believe himself loveable, as he tries to swagger his way towards dry clothes. In this brief scene the actor devastatingly captures the essential Benedick.

Beatrice follows on in another watery immersion. Their embarrassed wooing follows a funny, poignant route to happiness, accidentally aided by Mark Addy's Dogberry and Trevor Peacock's glorious, comiccut Verges, hovering on senility's verge.

The secondary plot, hatched by Andrew Woodall's depressed Don John and which almost destroys Claudio's love affair with Hero, fails to catch fire. Many directors nowadays stress the homoerotic camaraderie uniting Aragon's Prince, Claudio and Benedick, and which may explain the foul treatment of Hero.

Hytner plays it disappointingly straight, with Daniel Hawksford's bland Claudio, Julian Wadham's inscrutable Prince and Susannah Fielding's wan Hero failing to raise the temperature. It is Russell Beale and Wanamaker who make big, theatrical waves.