Twelfth Night, Barbican Theatre, London

They're awfully short on lyricism in the RSC's Illyria. Both Orsino's palace and Olivia's house are represented by a wall of battleship-grey shutters, and the box hedges in her garden are two solid slabs of municipal green that could repel an army.

Poetry, though, isn't the point in this production. Only 30 years late, Lindsay Posner has hit on the idea that Twelfth Night is a play about gender confusion, and the play is directed as if for schools of smirking teenagers. Attracted to Viola (disguised as the Duke's page), Olivia clamps her neck in an armlock a mugger would envy and rams their lips together. When, at the end, Olivia has married Viola's twin, Sebastian, she approaches her for a sisterly kiss. Instead or a tender brush of wonder and regret, there's a repeat of the grab and the smacker. All that's missing is a nudge and a wink.

A double bed is the focus of the scene between Sebastian and Antonio, the sea captain who saved him from the wreck that divided him and his sister. Half-dressed, they lounge, chatting, while Antonio nuzzles the boy -- well, he says later they have been together for months, day and night, so what else could that mean? After all, we know sailors.

Confusion isn't limited to sexual identities. When Olivia's steward, Malvolio, pursues the disguised Viola back to the Duke's house, it's disorienting to find that the decor hasn't changed. Though Ashley Martin-Davis's dark, empty set evokes no particular place or time, his costumes are Edwardian and, for the most part, as cheerless as the grey wall and grim garden. The Duke's servants wear dark, frogging-covered uniforms that make them look like department-store doormen in mourning.

The lack of sweetness is exemplified by Zoe Waites's Viola. Her hair is cropped and slicked down like a Weimar lesbian's, she walks like a duck, and her manner, instead of being tremulous (love of Orsino, fear of Olivia), is that of a country matron in a baying competition with her hounds. Ben Meyjes as Sebastian is her twin in charmlessness, and Mark Hadfield's Feste an irritant. A music-hall turn in big shoes and porkpie hat, he sings the play's exquisite songs in a way suggesting that, if music is any kind of food, look for the Alka-Seltzer.

The only pleasure comes from two actors one can always rely on. As Sir Andrew Aguecheek, Christopher Good is an adorably languid dandy, fingers dangling limp as faded lilies from the wrists he puts forward as proof of his omni-incompetence. The youthfulness of Guy Henry's Malvolio makes his torment by the jokers even more painful than usual – it seems more cruel to ridicule someone who hasn't had time to learn the ways of the world. But, tricked into believing his mistress loves him, he deliriously unravels into a frenzy of creaky grinning and capering. To see this stuffed-shirt's terrible imitation of happiness is to know the real thing.

To 9 March (020-7638 8891)