What a valuable week for observing how transsexuals and transvestite characters on stage blur the lines of gender and sexual identity! Hard upon Samuel Adamson's Old Vic adaptation of Almodovar's All About My Mother, Neil Bartlett has given Twelfth Night the serious cross-dressing treatment. Viola is startlingly played by a young man (Chris New). That model of swaggering, drunken machismo, Sir Toby Belch, and the weedy Sir Andrew Aguecheek are both comically dragged up - or rather down - in delightful parodies of upper-crust masculinity, by a gruff, bearded Majorie Yates and a vacuously jovial Annabel Leventon.

It ought to be a revelatory occasion, freshly reminding us of Shakespeare's piercing awareness of sexual ambiguity. Yet Bartlett, at his best when dealing with the nuances of concealed and revealed homosexuality, disappoints. He offers a cool, erotically superficial Twelfth Night that never captures the play's atmospheric undertow of melancholia or conveys the psycho-sexual disturbance that Viola and her twin bring in their wake.

Bartlett's Illyria, whose sea-sounds are never heard, vaguely conjures up late Victorian or Edwardian England, judging by New's grey knickerbocker suit, and Miss Yates's male attire. Kandis Cook's minimal, hugely unevocative, almost bare-stage design offers just a gold and black backcloth, with two mirrors and a grand piano, from which James Clyde's wide-boy Feste serves as a cynical master of musical ceremonies, swinging from Noël Coward to pop balladeering.

A male actor, playing first Viola and then the page Cesario, needs to be androygnous in appearance and manner to enthral both Orsino and Olivia. There is, though, scarcely a frisson of femininity about Chris New's eloquent, but far from grief-stricken Cesario and insufficient signs of wistful longing for the Duke Orsino (Jason Merrell). You could not accuse the bluff, bearded Merell, who never dares let slip the chains of heterosexuality except for a moment of manly hand-holding with Cesario, of being smitten or disturbed by this Cesario. Justine Mitchell's Olivia, who you would never guess has lost both a father and brother, cannot breathe intensity or sexual ardour into her scenes with Cesario, who backs away from her in bemused alarm. Even Antonio's passion for that indefatigable sexual tease Sebastian fails to materialise.

The comic-farcical elements work. John Lithgow's stately, black-garbed Malvolio, comic in his ponderous, affronted dignity and superciliousness wafts around in a trance of delight and pleasure when deluded into believing that Olivia has finally fallen for him. The extremity of Lithgow's emotion makes his downfall and exposure really effective. Annabel Leventon's Sir Andrew, a flaxen-haired, silly-ass, Michael York look-alike, braying with stupidity, and Miss Yates's splendid boisterously barking Belch alone justify Bartlett's listless cross-dressing experiment.

• Until 6 Oct (0844 800 1110).