The curtain rises on one of the most famous - and thrilling - images in musical theatre history. A long row of tapping feet, in perfect, noisy unison. As it rises further, we see the bodies belonging to those busy percussive shoes: the auditioning chorus for Pretty Lady, a new show that is going to electrify Broadway. It's such fun this idea of a show within a show, and it's the reason 42nd Street is the most sophisticated and joyful of backstage musicals. It simultaneously enables the audience to root for the young hoofers of 1933 who are staving off the breadline by flinging their talents into a flamboyant musical production - and to know that what we are watching is also a product of our own time, and our longing for escapism in an age of doubt.

The story couldn't be more simple. Julian Marsh, a legendary impresario is mounting a Broadway extravaganza; young chorine Peggy is called upon to save the day when grumpy leading lady Dorothy Brock breaks her ankle. "You're going out a youngster, but you've got to come back a star," he tells her, in one of the most sob-inducing lines in showbiz history. And of course she does.

By the time the stage show was originally constructed around this flimsy edifice in 1980, some of the moral complexity and darker undertones of the 1933 film on which it was based had been stripped away. The process of flattening and broadening has continued in this revival, directed by Mark Bramble, which has designs by Douglas W Schmidt and Roger Kirk that are even brasher and brighter than before, with mixed results. For example, oddly, for the wonderful "We're in the Money", the green and white dollar flavoured costumes are now just white and gold, which reduces rather than increases the razzle dazzle effect.

But the greatest casualty is the delivery of the book - which is strange, since Bramble wrote it. You can just about forgive pop legend Sheena Easton, who gives a game but entirely wooden performance in her West End debut as Brock. She is a singer, not an actress, and she finds emotion only when her still lovely voice floods out. It is stranger to find everyone else rushing through the lines as if they have no meaning, including the vastly experienced Tom Lister (of Emmerdale fame) as Marsh, and the youthfully appealing but uncharismatic Clare Halse as Peggy.

The best performances are all around the edges, from Jasna Ivir as the wise-cracking Maggie, Christopher Howell as Bert, and Emma Caffrey as Anytime Annie, the girl "who said no once and then she didn't hear the question."

This weirdly doesn't matter, because no one goes to 42nd Street for Shakespearean depth of emotional expression. What you go for is an endless catalogue of catchy songs from "Lullaby of Broadway" to "Shuffle Off to Buffalo" - by Harry Warren (music) and Al Dubin (lyrics) - and tap routines so vigorous they make your fillings rattle.

On this front, the show delivers big time; the razzmatazz of the staging is so preposterous that it makes you smile, especially when it is delivered by a chorus drilled with pure precision in choreography remounted by Randy Skinner from Gower Champion's original.

Within Pretty Lady, you get everything but the kitchen sink: dancing flowers, Busby Berkeley beauties reflected in a gigantic overhead mirror, high-kicking chorines, and finally, blissfully, a golden-lit stairway to heaven with everyone singing and hoofing away as if their lives depended on it. It is, in my book, impossible not to like.

42nd Street runs at the Theatre Royal Drury Lane from 4 April.

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