Ethel Merman is literally inimitable: she projected, through a voice of molten brass, a unique personality that was both tough and tender. But the justification for John Kane's richly enjoyable Merman tribute is that it reminds us of a Broadway career spanning 40 years and enables us to rehear some great songs without amplification or fussy orchestration.
The format is simple: we watch Merman in 1961 rehearsing a Las Vegas cabaret show that anthologises her past. We not only get to hear standards by Gershwin, Porter and Berlin, we are also constantly reminded of Merman's consummate professionalism. When the director pleads that the audience wants to see Ethel Merman the woman, she crisply replies: "Send them to my gynaecologist." But we also learn that the downside of her implacable self-belief was a certain unapproachability. "Ethel," remarks a fellow artist, "has a great relationship to the audience. You just feel she's never been introduced to the cast."
As anyone lucky enough to have seen Merman at the London Palladium will know, you can't reproduce her iron precision. What you can do is evoke it, which David Kernan's production successfully does by dividing her into two. Susannah Fellows embodies the young Merman and, although she is infinitely sexier than the original, she displays a spry comic finesse and impeccable diction. And Angela Richards does a remarkable job as the mature Merman, reminding us how she always put technique to the service of a song. In I Get a Kick Out of You, Richards heightens the verb by prefacing it with a slight caesura and in the key numbers from Gypsy, she highlights the bright-eyed resolve of this mastodon of stage mothers.
At times, Fiz Shapur's accomplished pianist is made to seem excessively naive ("How many husbands did she have?" he somewhat recklessly asks). And I could have lived without the intrusion of a camp costume designer. But this is a good show that not only evokes Merman's artistry, but also reminds us that she helped transform Broadway leading ladies from demure innocents to tough and knowing broads.
· Until February 1. Box office: 020-7226 1916.