The course of true lust never did run smoothly, as Jonathan Kent's boisterous production of William Wycherley's sex-mad Restoration comedy keeps zippily demonstrating - though eros puts on a bit of a limp show.

The Country Wife launches with a bang the Haymarket's valuable new policy of presenting 12-month seasons of plays chosen by a different artistic director each year. The only disappointment is that six months of Kent's Haymarket tenure will be given over to yet another new musical. Still, it is good to see the West End taking a novel turn. Even if Kent takes too farcical approach to the play's sexual comings-on and goings-off, and the performances are not funny enough, there's no missing the appeal of Wycherley's cynical, mocking attitude to his generation of sex addicts.

Written in Charles II's free and easy 1670s, when London ladies and gentlemen took the threat of fatal syphilis lightly and often screwed themselves into early coffins, The Country Wife could just as well be a play for today, about our own sexual morality.

It was a sharp decision on the part of Kent and his designer, Paul Brown, to make those mobile sets, with plenty of farce-related doors, look modishly modern. The actors dress in a mixture of period and contemporary clothes, inhabit rooms with wallpaper that could have featured in the Standard's Homes and Property section, while Wycherley's young lechers about town play pool and read the Racing Post.

Kent keeps several plot lines running in several, sexually motivated directions, the best of them concerning Toby Stephens's preening, posing Mr Horner who pretends to have turned impotent so as to have innocent and free access to the best wives in town.

Interestingly Wycherley offers a portrait of women who come to Horner not in search of romance but simple sexual satisfaction. This anti-hero's gorgeous climactic "China" scene, perhaps the smuttiest in British drama, finds Stephens happily poised to be seduced by Patricia Hodge's far from farcical, yet too subdued and dignified Lady Fidget.

Her husband (bland Nicholas Day) bursts in and finds them in a position that looks far from innocent. The scene raises plenty of audience laughter but it ought to be funnier, sexier and dirtier than these three accomplished, but not that comic actors make it. Stephens, over-loud and blustering, quite misses Horner's sly philandering relish and malice.

The second and related plot line depends up David Haig's fanatically jealous Pinchwife, who keeps his simple wife Margery locked away in the country for fear of the likes of Horner. It can work to fine effect.

Haig, at his comic best with characters smitten by anger and desperation, here sometimes succumbs to repetitive fury syndrome, instead of giving a slow-burn performance. Fiona Glascott makes an embarrassingly infantile, almost grotesque Margery.

John Hopkins's suave Harcourt, in a third sex-tangle, manages to wrest Elisabeth Dermot Walsh's Alithea from Jo Stone-Fewings's unamusing Sparkish, wins laughs by playing dead cool. Kent's production made me laugh a lot but it needs more comic invention to work.

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