First Night: Postcards From God, Jermyn Street Theatre, London

Wimpled warblers are currently big box-office at London Palladium, where the tills are alive for the hit revival of The Sound of Music. The cash registers look set to be somewhat quieter for this new musical ("like nun other") about Sister Wendy Beckett. The contemplative recluse and TV-star art critic seems to have renounced her media career and retired for good to her other life of prayerful silence and solitude as a " consecrated virgin" in a caravan in the grounds of a monastery.

But Postcards from God - the Sister Wendy Musical has elected to thrust her back into the limelight as the focus of an off-West End tuner.

The phenomenon of Sister Wendy is full of apparent contradictions (the solitary who is also a celebrity; the career-celibate who waxes rhapsodic about erotically charged art, etc). A piece which places a supposedly publicity-shy nun centre-stage in the most showbizzy of genres could have operated as a vehicle for satirically heightening a sense of these incongruities. But that's not how it works out in Postcards from God, which would be a disappointment to Sister Wendy's detractors such as Germaine Greer, who consigned her to Room 101, and the doyen of art critics, Robert Hughes, who dismissed her as the "relentlessly chatty pseudo-hermit with the signature teeth".

True, it may be garnished with feebly skittish attempts at camp send-up, performed, to a lone piano accompaniment, by a multi-tasking all-female cast who have to breeze their way through a resolutely uninspired score by Marcus Reeves that spoofs everything from gospel and rock'n'roll to rap. But Postcards from God is essentially a cloying celebration of the woman once described at "the rabbit in a habit".

At one point, there's a direct allusion to The Sound of Music in the scene where Mother Ruth (Andrea Miller) gives Myra Sands' permanently beaming Sister Wendy permission to go out into the world to fulfil her destiny of spreading the gospel of art: "This life is not all whiskers on kittens and raindrops on roses/ This life is governed by God and what He proposes".

But, as conceived by Reeves and his co-writer Beccy Smith, Sister Wendy may remind you of another Rodgers and Hammerstein song: she's just a nun who can't say no - and if it comes with the territory of exercising her God-given talent, then she'll simply have to grin and bear such drawbacks as being the champagne-quaffing centre of attention, signing autographs, and appearing on an American chat-show that invites the audience to "touch a celebrity".

"Sister Wendy, play the game/Do you really relish fame?" the hack pack ask her here, but this musical treats the idea that she might have been having it both ways as beneath serious consideration.

The cast poke their heads through flaps in the pop art set to conjure up the paintings (by Hopper, Guercino, Warhol, et al) upon which "the Nun, Critic, Superstar" meditates in song. Some of these sequences are moodily evocative but the piece is too hamstrung by its own contradictions as a musical-tease-cum-hagiography to resolve the Sister Wendy paradoxes.