Sarah Wildor, 25 going on 13, taking temporary leave of absence from the Royal Ballet to dance the role of Cinderella in the West End, is doubly gagged by secrecy. She's even brought the company manager along to make sure she keeps mum. How can the plot of a well-known fairy story possibly be under embargo, you may ask. When it's been AMP'd, it can. Following the stupendous success of Adventures in Motion Pictures' reworking of Swan Lake (who could have predicted that shattering denouement?), everyone, but everyone, wants to know what choreographer Matthew Bourne will do with Cinderella.
Wildor will divulge this much: it's set in London during the Blitz (which also happens to be when Prokofiev wrote the score). Doodlebugs and gas masks replace pumpkins and mice as the currency of domestic life. The ballroom has been bombed out. The ugly sisters are played by girls. And there are ugly (well, not so ugly) brothers as well, plus a particularly devastating stepmother, played in the first cast by Lynn Seymour. The prince (Adam Cooper, sporting pencil moustache) is a dashing RAF pilot. Cinderella, wait for it, is a frump.
"I'm used to the Frederick Ashton version of course," says Wildor, whose entire professional life until now has been with the Royal Ballet. "At first I couldn't imagine anything more appropriate, more musical, than that. But Matthew [Bourne] opens your eyes to new possibilities. His ideas are so vivid, you're continually thinking yes! Good God, that's perfect! Why hasn't anyone thought of that before?"
As one of the Royal's most versatile young stars, she has scorched a rapid path through the classical repertoire. Her tiny build and porcelain pale-blonde looks have made her a natural for Juliet and Giselle. But more startlingly she has proved herself in testing dramatic roles. She made a sizzling Manon, and last season her powerful performance as MacMillan's Anastasia left audiences tearful and shaken. Yet oddly enough only once has she been partnered by Adam Cooper, her boyfriend in real life, and that was in MacMillan's bleak The Invitation, where she played a fresh young thing, raped by his ageing roue. So it comes as "rather a nice change, a very very nice change" to be working and dancing with him daily, with romance thrown in to boot.
But whereas Wildor's exeat from the Royal is strictly temporary (she's being allowed six months out, with Anthony Dowell's blessing), Cooper has burned his boats. Following the dazzling success of AMP's Swan Lake, which turned out to be the longest-running ballet production ever to play in London, he quit the Royal Ballet earlier this year to star in the Los Angeles run of the show (another sell-out). The company has been tight- lipped about his departure, and Cooper in turn has been free with his criticism of the Royal Ballet - that it fails to offer its star dancers sufficient challenges, for instance. All of which might seem to make Wildor's current position more than usually delicate.
"Not at all," she says. "I've been very very lucky with the Royal Ballet and I'm very happy there. Whereas Adam originally had to be coerced into ballet and now wants to do other things, I've always known I wanted to be there and that hasn't changed. I didn't fight to get out of the door or anything. It's just that this invitation came up."
What happens if - more like when - this Cinderella runs and runs? Will she be tempted to loosen the ties with classical dance? "Cross that bridge when we come to it," she says, which sounds like something someone has told her to keep on saying. At any rate, she religiously wears her pointe shoes to the hour-and-a-half class she takes every morning with the rest of the cast. "I'm the only one who wears them and they must think I'm a bit of a nutter, but it keeps my feet strong so that when I go back to the Royal Ballet next February, I'll still be reasonably on form."
If AMP's eclectic modern-dance style is quite different from anything she's done before, what is familiar to her is the way Matthew Bourne fuses movement and emotion into one seamless whole. It puts her in mind of Kenneth MacMillan, the choreographer she was just in time to know in person before he died, and whose complex heroines have been her biggest challenges to date. But whereas she might get a crack at Juliet or Manon once or twice a season, a West End production like this runs six nights a week. Thus Cinderella, like Swan Lake, will be triple-cast, and two other AMP dancers - Saranne Curtin and Maxine Fone - are shadowing Wildor in the title role.
"They probably look at me and think - oh dear she's really classical," says Wildor, who, off-stage at least, seems to be the sort of star that might apologise for twinkling too much and spoiling a nice dark sky. "But the great thing is that all the movements Matthew devises can be done in the way that suits each of us best. That means that all three Cinderellas will come out slightly different. And the best thing of all," she enthuses, "will be living with this role over a long period. People tell me I'll be able to develop it and grow with it. I'm looking forward to that."
All very well, but the thing my six-year-old daughter is burning to know, I tell her, is whether in this version Cinderella gets to wear a sparkly dress. "Yes she does," blurts Wildor, then casts an enquiring look at her minder. "I am allowed to say that, aren't I?"
! 'Cinderella': Piccadilly Theatre, W1 (0171 369 1734), now previewing, opens 7 Oct.