This award-laden New York production of Rodgers and Hammerstein's 1949 classic arrived in London with the news - announced on stage by the show's American director Bartlett Sher - that its new leading lady, former EastEnder Samantha Womack, would soldier on despite a broken toe. It was a brave decision. There is stomping to be done during I'm Gonna Wash That Man Right Outa My Hair; and there are kicks and Popeye-style shanty steps required for Honey Bun, the joke number for which Womack's Nurse Nellie dresses as one of the US marines based on a Polynesian island during the war.

Womack negotiates the moves with barely a hint of the pain she must have been going through. If you were to look for reasons as to why the first act of South Pacific is so life-sappingly slow, the strapped Womack toe would not be among them. You would instead have to look at Joshua Logan and Hammerstein's creaky book which is based on James A Michener's Pulitzer-winning novel Tales of the South Pacific.

It is a story we join two weeks after Nurse Nellie, a small town girl from Little Rock, first met French plantation owner Emile De Becque, played by the tender baritone Paulo Szot who on this evidence richly deserves the award he won in New York. Yet rarely has a whirlwind romance felt so protracted. By the end of the first act, just two things of note have happened. It has emerged that the newly arrived Lieutenant Cable (Daniel Koek) is on a dangerous mission to spy on the Japanese navy, a job for which he plans to enlist Emile's help; and Nellie has done a runner after discovering that the Frenchman she loves has two children by a black woman who is now dead. It is the colour of her skin she objects to.

Though not much happens, it happens to a brilliant score. The moment Emile and Nellie met is unforgettably preserved with Some Enchanted Evening; the frustration of sex-starved sailors explodes with There Is Nothin' Like A Dame and the eerie call of the wild that is Bali Ha'i is sung with a siren's lure by Loretta Ables Sayre's, Bloody Mary.

But for a generation who would have first heard Some Enchanted Evening not at the theatre, but more likely hummed by their grandmother, the songs feel attached to a morality tale that manages to say the bleedin' obvious about racism while oddly ignoring some pretty urgent side issues.

Sure, it is great that Emile saw skin colour as no barrier to a past relationship. But it is not easy to empathise with him when Emile's response to a girl who is revolted by his colour blindness is to send her flowers.

And when, smitten by Bloody Mary's delicate daughter, Lieutenant Cable rails against the racism that separates them with a cry of "Why can't I have her as my wife?", I wanted to cry back, "Because she looks about 12?"

Sher's is undoubtedly savvy to this. With one look, the black American sailors on the island condemn Nellie's attitude. And when Bloody Mary offers her daughter to Cable while singing Happy Talk, the mother's proposal of marriage sounds more like an offer from a pimp. But being savvy to the issues is not the same as resolving them.

Still, as you would expect in a production directed by the Metropolitan Opera's Sher, the singing is beautiful - mesmerisingly so in the case of Szot. But that just adds to the sense that South Pacific is better off in concert form, such as the 2005 Carnegie Hall show that led to this revival.