Size really does matter in Rob Young's monologue about a man from south London who is suffering from Proteus syndrome. John Dixon is ordinary in every way - in his desires, his needs, his everyday concerns. But his penis is 102cm long, contains almost three litres of blood and comprises 50% of his body weight. The stirring of an erection starves his brain of oxygen, causing near-fatal blackouts. For John the orgasm is not a little death but the big one.

In the circumstances, John is not a man to rub up the wrong way. He censors every aspect of his life to avoid erotic stimulation but cannot censor his need for love. Reading the small ads in Loot is a wild thrill for John. Then he meets Ruth, a tart with a heart from Stockwell, who takes one look at what's in John's shopping trolley and whisks him off to Hastings, where John gets that floating feeling that means it must be love.

It is hard to write about this hour-long show without resorting to the puerile because it takes itself so seriously, failing to acknowledge that there might be something even remotely funny in John's predicament. The real wonder is that a piece of writing so absurdly small should have made it on to the stage in the first place.

But Simon Vincenzi's clever production, with its fleet of glowing red Zeppelin-style organs hanging from the ceiling, its aching lighting and strange, unsettling soundtrack, gives the evening an extra dimension and a weightiness that the piece otherwise lacks.

There is a marvellous performance too from Laurence Harvey, who stands immobile like a beached whale for the whole performance and whose understated, deadpan delivery conveys all the bemused pain of a very ordinary man in an extraordinary situation.

• Till April 1. Box office: 0171-928 6363.