THEATRE Stanley, Cottesloe Theatre

If everything in life is holy, then this must include extra-curricular sex. It's a point that's not been wasted on the David Koreshes of this world. Being calculatedly wacko in Waco is very different, though, from being sublimely cuckoo in Cookham, as the life of the artist Stanley Spencer aptly demonstrates.

Pam Gems's overlong but very funny and affecting play about the painter never doubts that he was utterly sincere in believing in the sanctity of his sex life, a belief that involved wanting to have two wives on the go at once. In fact, it shows that everyone concerned would have had a much easier time of things if he'd been a hypocrite.

The play is keenly alive to the potty, painful comedy of his complicated marital arrangements. His newly divorced first wife and soulmate, Hilda, finds herself begged to come back as his mistress when wife number two, a snooty, towering virago, abandons him and returns to her lesbian lover. If this lot could have taken their troubles to Relate, you feel the entire staff would have opted, on the spot, for early retirement.

What the play makes you understand, though, is that Stanley's selfish purblindness to the needs of nearest and dearest is somehow part and parcel of the paradoxically monomaniacal generosity of his art. In its charmed universe, where Christ relives his career in Cookham and lumpy, clumsy creatures achieve the levity of transfiguration, everyone is saved at the final judgement. Which is both charitable of Stanley and not exactly lacking in blinkered ego either.

John Caird's production beautifully judges the balance of all this. With the colossal Resurrection (not yet finished) on the back wall, tiers of scaffolding and part of the audience in pew-arrangement seating, the Cottesloe is transformed into a sort of secular cathedral. While Stanley and his second wife choose sexy underwear in a posh shop, a swelling church organ in the background acts like a cheeky aural pun. The spirituality of Bach steals over scenes that would give a devout Lutheran a heart attack.

The performances are spot on. There's more than a hint of another Spencer (Diana; Wales, Princess of) in the spoilt Sloane vowels of Anna Chancellor as spouse two. Can this woman have been quite the monster the play paints her? Deborah Findlay's wonderfully moving performance as the first wife prevents you from ever condescending to her self-destructive devotion to the artist. It's significant that Spencer feels closest to her when she's safely dead. Antony Sher's splendid Stanley - a bespectacled nerd with a garden gnome hat and trainspotter clothes - is never more than two steps away from being beside himself with fanatical, maladroit rapture. You completely believe that here's a man who could marvel for hours at the beauty of wood-lice in the loo.

Booking to 30 March: 0171-928 2252