Guys and Dolls, Piccadilly, London

What's luck got to do with it anyway?

You might be able to rock the boat but you can't sink this baby. Frank Loesser's great musical from 1950 is hilarious and lovable in its depiction of Broadway low-lifers - the scurrying gamblers, the eternally affianced showgirl with a psychosomatic cold, and the Sally Army sergeant letting her hair down. Almost every number is a corker, from the harmonious floating romance of "I'll Know" to the screwball medical patter of "Adelaide's Lament" (the ditty about streptococci). Swerling and Burrows' co-scripted dialogue is ebulliently witty too.

You might be able to rock the boat but you can't sink this baby. Frank Loesser's great musical from 1950 is hilarious and lovable in its depiction of Broadway low-lifers - the scurrying gamblers, the eternally affianced showgirl with a psychosomatic cold, and the Sally Army sergeant letting her hair down. Almost every number is a corker, from the harmonious floating romance of "I'll Know" to the screwball medical patter of "Adelaide's Lament" (the ditty about streptococci). Swerling and Burrows' co-scripted dialogue is ebulliently witty too.

So, it is surely a safe bet that Michael Grandage's new West End production - starring Ewan McGregor as Sky Masterson - will be a hit.

There is plenty to celebrate here. To begin with, the Manhattan skyline (as designed by Christopher Oram) is dazzling, with a stack of skyscrapers glowing in the dark, a golden bulb in each window like theatre-billboard lights. Also, Rob Ashford's choreography responds brilliantly to dramatic and stylistic shifts in the music. The big Latino number when Jenna Russell's religiously prim Sarah Brown is whisked off by Sky for one wild night in Havana is an absolute blast.

Caught up in a whirl of lusty locals, Russell's mix of rigidity and drunken reeling is terrifically funny as she is swung under a stranger's crotch, or as she lurches off a pumping hip to flop over like a merrily wanton rag doll. The clandestine game of craps, down in the sewers, is also an enjoyable medley of sharp jazz moves and cod-balletic pirouettes, as the short fat mobster, Big Jule, builds up to throwing the dice. As for the songs, what comes across strongly is Loesser's brilliant ear for catching street sounds and speech rhythms and translating them into music.

Setting aside the movie with Brando and Sinatra, staging Guys and Dolls is a risky venture when Richard Eyre's storming National Theatre production still lives in the memory of most musical fans as a show that left you walking on air. By comparison, Grandage's production often falls somewhat flat. The costumes are on the drab side: a lot of faded browns which might be realistic but sap the characters' brio.

More importantly, from where I was sitting, the orchestra sounded as if they were all trapped in one loudspeaker to my left, and they still managed to drown out Niall Buggy's Arvide who seems to have wrapped his hymning vocal cords in some vast invisible muffler. In fact, no one's voice is going to blow you away here, except when everybody choruses on mass. Though McGregor was applauded for Moulin Rouge, his singing sounds nervous on a large stage, reverberating tinnily in the roof of his mouth. Perhaps he will enjoy himself more with time, but he is currently just blandly pleasant. In fact, Sky's final conversion from the criminal underworld to banging Sarah's Christian drum barely seems a comedic twist here because McGregor exudes all the bad-boy vibes of a nice-looking vicar.

Still, he and Russell are romantic, falling irresistibly into each others' arms. Big, burly Martyn Ellis gets everybody swinging jubilantly with "Sit Down You're Rockin' The Boat". Jane Krakowski's Adelaide and her showgirls are cheeky and charming in their striptease with white mink stoles, and Douglas Hodge's Nathan Detroit - desperately trying to give the cops the slip - manages to be huggable and highly animated, lumbering around like a saggy-bellied brown bear. He emerges as the real star of the show. Flawed but still fun.

k.bassett@independent.co.uk

To 1 October. 0870 060 0123