Inconceivable, West Yorkshire Playhouse, Leeds

It must have been quite a culture shock for Duncan Bell. One minute, he's playing Swann in an arty production of Harold Pinter's Proust screenplay; the next, he's whamming out knob gags in a populist piece by Ben Elton. But if the experience has left him feeling flustered, this has fed fruitfully into a fine performance of harassed charm and hapless subterfuge as the TV producer with fertility problems in Inconceivable.

This stage show is the third manifestation of the material. I'd read the novel but didn't check out the movie until after seeing the theatrical version. It was a useful exercise because it helps to highlight the virtues of Lawrence Boswell's deft and fleet-footed adaptation.

The film haemorrhages its credibility by being stuffed with British comedy superstars turning in strenuously determined cameos. You'd pay again to look anywhere but at the screen when Dawn French does her walk-on as an Australian nurse who packs the hero off to a cubicle for a "five-knuckle shuffle", or when Emma Thompson hoves into view as the New Agey hippie woman who orders the couple to make love on a ley line. And the central pair are too glossily presented: you feel they would cut their losses and buy a child from Bosnia.

None of those distractions and irrelevances bedevil Boswell's theatrical account: a skilled, characterful company play multiple roles and unite to form a hilarious spoof of a Greek chorus, enfolding themselves in the green cloth they have laid out for the couple's moonlit bonk on Primrose Hill and miming synchronised snarls as the furry creatures who thwart the post-coital bliss.

In the novel, Sam and Lucy tell the story alternately in their diaries ­ an authenticating epistolary device that does not quite disguise the fact that Elton, like Nick Hornby, has trouble sustaining a female voice. In the theatre, this convention translates naturally into direct-to-audience address, and Boswell stages the couple's movements so that we see, with often diagrammatic clarity, how the indignities of infertility have made this marriage a double act of individuals increasingly isolated from each other. Sam is betraying his marriage by secretly plagiarising Lucy's diaries for a Britcom movie about infertility; she is smitten by a dishy actor. It's typical of the staging that a guilty long-distance phone call is presented with the mentally estranged couple sitting side by side on the marital bed. Or a hospital scene will shift instantly from real life to the movie studio where it is being cannibalised for fiction.

The pale, elfin Geraldine Alexander gives an accomplished performance as Lucy, shifting with no screech of gears between the knock-about humiliations of a life in which sex has lost all its spontaneity (the bed joylessly rises and falls through a trap or drops to give us a bird's-eye view) and moments when she quietly communicates the empty, desperate ache of the childless. The production, whose speed and humour are enhanced by sometimes terrific graphics, manages to be buoyant without falsifying her pain. There's a good feeling about the show, but it's not gratingly feel-good.

To 16 June (0113-213 7700)