Glorious! Duchess Theatre, London

Great material, classy acting, shame about the play

There aren't many totally talentless people who can say they have packed Carnegie Hall to the rafters (and at the age of 76 to boot). Certainly, a fascinating play could be written about this daughter of a Pennsylvania banker who forbade her to sing in public and then left her the wealth that enabled her sing wherever she liked. Glorious! by Peter Quilter is not that work.

Indeed, the humourless will say that it ironically mirrors Foster Jenkins's own reverse-alchemy effect: it takes top-rate material and produces one uninhibitedly duff note after another. But, also like the singer, it is supremely good-natured and infectiously joyous as it dispenses gags that are so Are You Being Served? in style, the show could be subtitled "Are You Being Serenaded?"

Maureen Lipman is majestically on song (so to speak). Lobbing carnations into the audience or decked out in tulle, tinsel and wings as the Angel of Inspiration, she may have a smack of Dame Edna, but the essential difference is the beatific, touching sincerity with which this diva massacres the music.

In the Queen of the Night's aria, she makes desperate barking yelps like a poodle being tortured as she strains for the coloratura high notes. It's at once hysterically funny, an amazing technical feat by Lipman, and strangely moving. As with Don Quixote, there's magnificence in this degree of delusion.

It was a gift, you feel, to be so pottily focused that she could shut out the noise of mocking laughter or interpret the pandemonium in the audience as the equivalent of Frank Sinatra's screaming bobby-soxers. This stout matron is both foolish and inspirational: "a symbol to all those who dreamed and didn't dare".

In Alan Strachan's witty, handsome production, Lipman is surrounded by a highly engaging team of first-rate comic talent. William Oxborrow is wonderfully dry and droll as her young gay accompanist, who gives rise to an unceasing stream of laboured innuendo: Cole Porter, he's told, always comes to her concerts "with a huge bunch of pansies".

And Josie Kidd is delicious as her ditzy socialite friend, Dorothy. Yes, Florence was a friend of Dorothy without being "a friend of Dorothy", though accompanied by one, if you get my gist (nudge, nudge). And although scarcely relevant, Dorothy's dog does provide one of the best jokes.

I think an Alan Bennett-type monologue - like the one with Julie Walters as the actress convinced she was filming an art movie that was obviously a porno flick - would be the best way of capturing Florence's delusion. But Quilter's entertaining, revue-like ragbag of a piece has its depths too, as in the sad, unearthly final sequence, where you see the diva circle about, ravished by the sound of an authentically glorious voice. You realise what she was hearing inside her head when she sang.