Strong and sexy: McCartney's designs have always walked the line between street tough (such as spring 2002, left) and the softly romantic (fall 2002, right).

(Stella McCartney, cont'd)

The first item Stella McCartney designed was a jacket when she was 12. "My mum was a huge influence," she says. "The true fearlessness in the way she held herself, in life and in every way. To me, it's the most modern way to be a woman — a very real kind of femininity. My mum was like grunge before it happened. She never wore makeup. She used to cut our hair herself — really short and uneven." She rolls her eyes. "Thanks for that, Mum!"

She organized a stint working for Lacroix when she was 15 ("I don't think I got anywhere near holding the pins -- I was lace and shoes"), and during her time at Saint Martins, she did an apprenticeship at Savile Row, inspired by the men's suits her mother had worn. In the process, she acquired an aesthetic that subsequently charmed the fashion world. "That thing that Stella does, mixing soft, drapey tops with masculine tailoring, has been extremely influential. And she has a great feeling for the street," says Kal Ruttenstein, senior vice-president of fashion direction at Bloomingdale's. "It's absolutely how women want to dress," agrees Ana Abdul, of Language, in Nolita. "You put on a Stella creation and you feel really feminine."

If she's not Yves Saint Laurent, as her critics like to point out (Lagerfeld, in his inimitable way, called her "a T-shirt designer"), then she doesn't claim to be. Not being avant-garde is part of the point. Despite costing hundreds, sometimes thousands, of dollars, McCartney's clothes seem youthful and somehow accessible, as well as hugely desirable. Paltrow pinpoints the appeal of McCartney's trousers: "They're fabulous — the fit, the cut. They're just very sexy." At Chloé, McCartney increased turnover 500 percent. The creative director of Gucci, Tom Ford — no slouch when it comes to taking commercial bets — will be counting on a similarly impressive performance at her own label.

That, in part, was why the grim reviews for her first eponymous collection were so unnerving. Either in the hope of doing something memorable for her new label or out of sheer panic, McCartney, who'd become a reliable source of lovely, easy-on-the-eye garments, chose this moment to replace her stock-in-trade flirtiness with something more hard-core. Though it was hardly her fault, the timing was terrible, too: a month after September 11. She showed tiny panties with the word wet picked out in glitter across the crotch, together with suits with TROUBLE AND STRIFE (Cockney rhyming slang for "wife") stenciled down the sides. For musical accompaniment, she chose "Give Peace a Chance," instructing her models to give peace signs to the audience — who subsequently looked as though they'd had vomit dished over them.

"It was badly presented," she says with the benefit of hindsight. "I was scared and trying too hard." In some ways, though, the criticism was an odd compliment: She'd created such a demand for her aesthetic that there was hell to pay when she didn't deliver what was expected. But it wasn't an ideal start. Some orders were canceled, though as Linda Dresner, of the trendsetting uptown boutique, notes, "The press aren't as influential as they think. You can have terrible reviews, but sometimes it just makes customers more curious. They want to see for themselves."

These days, McCartney isn't taking any chances. Her last show, in March — the labors of which are filtering into the stores now — saw a return to what she does best. For at heart she's a people pleaser (she says throwing parties terrifies her because she can't cope with being responsible for everyone's good time). And it's easy to forget that setting up a global business is a weighty matter for a young woman of 30. "It's a lot of responsibility," she acknowledges. "I've got employees." James Seuss, her CEO, says it was her employees McCartney felt worst about when the reviews appeared after the show last September. According to Seuss, she apologized to them all the next day. And then, says McCartney, she went to see Ford: "He was really sweet. He's become a good friend, and he gets it."

Ford's support must have seemed like a godsend after Chloé, where McCartney felt underappreciated (and, according to industry rumor, underpaid). "There were a lot of things I didn't get credit for," she says of her time there. Certainly, the press has had fun pitting her against Phoebe Philo, her onetime collaborator and successor at Chloé. "Part of me would love to talk about the jobs I've been offered, but it would piss everyone off even more," she continues. "But the first time I got headhunted, by a famous house, it was six months into Chloé, and it was like, 'Oh, my God, it's not just my dad — I am actually getting headhunted.' "

It may be that McCartney has never fully come to terms with her famous name, but perhaps she won't have to. "She's fresh, and women love her clothes — and that has nothing to do with who her father is," says Dresner. "What Stella has to figure out now is, where next?"

"I'm working on it," says McCartney.

For his part, Ford knows exactly where she's going. "She has everything it takes to be successful — the drive, the will, and the intelligence," he says. "She has great style, great taste. And she worries about the sales and thinks about the brand as a brand."

The brand is what's making planning the flagship store so difficult and so engaging for her. "It would be so easy for me to do a pretty shop with a chandelier and a vintage, upholstered chair," McCartney muses, "but I want to do something more interesting. I have to move forward." She won't divulge exactly how this will manifest itself in the store, only that it will surprise people.

That her first store is in New York is serendipity, she says: "We didn't plan it. That's just where a site came up first, but I'm thrilled. I spent a lot of my childhood here, seeing my mum's family. We even pronounced some words in American — all very exotic."

It's very useful, too, this birthright of those born to an international lifestyle. Unlike those of many European designers, McCartney's clothes work as well here as they do anywhere else in the world. "I feel very American," she says. "I have two passports — British and American." How chic, I say. "How expensive," she retorts quickly. "It means you pay twice as much tax!"