Ivor Novello's last musical proves a frothy and fascinating fiasco with lovely songs, wonderful lyrics (by Alan Melville) and a knock-out performance by dynamic, effervescent Sophie-Louise Dann as Gay Daventry, a big musical theatre star on the way down in Manchester.

The role was written for Cicely Courtneidge, renowned for the first act closer, "Vitality," here done more andante than allegro, but captivating all the same: a well-drilled chorus, a doughty pianist (James Church), and Dann leading the paean to the secret of all success to rhyme with finality and practicality.

One of her fellow artistes, Linda Severn (the soprano role written for the recently deceased Lizbeth Webb) saves her bacon with a gift of £2,000 to found a drama school in Folkestone where, despite the intervention of a couple of smugglers and the hilarious bitching of a quartet of impecunious teachers - Myra Sands, Eileen Page, Gaye Brown and Elizabeth Seal (who was in the original 1950 production, shortly before she starred in Irma La Douce) - a Lancashire let-down is somehow transformed into a firecracker on the Kentish coast.

Stewart Nicholls' guiltily enjoyable production doesn't really define the switch in location, nor does it fully articulate the twists in the plot (the auction scene, the departure of the smugglers, the romantic resolution; all that is a terrible mess) but the show's still irresistible.

Why? Novello was a genius composer saddled with terrible libretti, usually his own. Here, he sends himself up, notably in the two opening numbers (of the Ruritanian "flop") as well as writing some simply gorgeous solos and chorales as well as delightful revue numbers (the teachers' item and the joyous "Bees Are Buzzin').

Helena Blackman's soprano is a bit tinny for the Lizbeth Webb numbers, but she outlines them charmingly, and her beau, a gawky rich kid who wants to be an actor, ingratiatingly played by flaxen-haired Josh Little, matches her pitch and performance temperature exactly. The production might be messy, but it's not crude or sarcastic.

No-one seriously interested in British musical theatre will want to miss Gay's the Word, nor Sophie-Louise Dann's high-voltage performance (before she crosses the channel to play Dot in Sunday in the Park with George in Paris); and there's even a last-minute cameo appearance from Frank Barrie, an actor for whom the word "stylish" is almost insultingly inadequate.

The evening's a treat, but nay-sayers are allowed too much leeway in the moulting slackness of some sequences, the lack of discipline in Richard Stirling's adaptation, and the colourful but fudged design of Gregor Donnelly. A Jermyn Street gem, no doubt, but no way good enough, alas, to reclaim a West End berth in a "proper" theatre.