Moufarrige, meanwhile, a handsome, patron type, sits in the corner of the room and observes the situation impassively. He then makes a minute gesture to one of the ateliers and a bolt of nude chiffon is brought in to protect Goff�s modesty. Stella looks like she might explode in frustration. "But it�s so fucking easy to get G-strings!" she cries, running her hands through her hair and chomping furiously on a piece of gum. "We�ve all got a pair sitting at home�" she says, flashing a look at her chief design assistant and best friend, Phoebe Philo, who shrugs in helpless agreement, "�haven�t we, Phebs?" It is Moufarrige who wins the battle, of course, and to Stella�s credit she does accept defeat� but only just. "It�s fine, it�s the autumn collection," she says dismissively, "but if this was spring, no way would I have agreed."

Such is the life of a young, strong-willed designer employed by one of the most traditional fashion houses in Paris. But what a long way McCartney has come from the days of her tiny, groovy Notting Hill showroom, when it was just her, Phoebe and the clothes, and if it was sunny, well hey, babe, why not get into a bikini and work from the garden? Perhaps not quite at the stage where people refer to her father as "Stella�s dad", Ms McCartney has nevertheless become a true star in her own right at the age of 27, with her fourth collection for Chlo� dubbed by most of the press as her best yet, and sales at the once-ailing house supposedly increasing five-fold since her arrival just under two years ago.

A month or so earlier, Natasha Richardson, Janet de Botton, Lord Hindlip and American Vogue held a glittering fundraiser for Aids research at Christie�s. Tout London had been invited and a group of guests standing in a corner decided to play that parlour game of the moment. If a bomb exploded right there and then, killing everyone in the room, whose face would be splashed across the tabloids the following day? Quite a few people plumped for Elizabeth Hurley. Hurley, meanwhile, nominated Stella McCartney, who turned up in aviator-shaped Chlo� sunglasses and a tailored suit with nothing but that aforementioned G-string underneath, making peace signs to everyone.

Those in the Chlo� loop include her friends Kate Moss and Liv Tyler, Cameron Diaz and Madonna, but also � and this is the key to her success � plenty of other women far less famous and rich who want to buy into that cool, Portobello Road-meets-Paris world of Stella McCartney. As Milan Vukmirovic, artistic director of Colette, Paris� trendiest clothes store, says, "Her air-brushed T-shirts were like freshly baked baguettes. Less than 24 hours after we put them in the window, every single one had gone." Which all bodes well for the opening of a Chlo� boutique in London, planned for late 1999 or early next year.

Of course, it might just be a matter of time before the House of Chlo� completely comes round to Stella�s way of thinking. The grey carpet and "revolting Eighties d�cor" were ripped out long ago, replaced by bleached wooden floors, a mad blue chandelier Stella picked up at Clignancourt, and an entire wall covered in hundreds of faces cut out of magazines � among them Andrew Lloyd Webber�s Celine Dion�s and Jackie Stallone�s � which the girls have mischievously entitled "the crazy freak zone". Most of the telephones, meanwhile, have little "ban fur" stickers on them. A strict vegetarian and PeTA supporter like her mother Linda, who died of breast cancer last year, Stella had it written into her contract that she never has to work with fur or leather. Chlo� still sells leather accessories, of course, but as Stella puts it, "I don�t need to see them." As for the runway shows, all the shoes are made of vinyl or plastic, all the bags and belts of fabric or raffia.

She herself is wearing a flowery Chlo� dress from a past season, with the arms ripped off so the edges are fraying, no bra, a pair of grey trousers and Adidas Stan Smith sneakers. All of which is perfectly offset by a deep freckly tan from a recent trip to Jamaica, and a huge diamond bracelet on her wrist, a present from her father. Her accent, meanwhile, is impeccably Estuary, with not a hard "t" to be heard anywhere.

Far less bosomy and pouting than her pictures would suggest ("I�ve lost a lot of weight recently, so my tits have shrunk") with stark blue eyes and a vague self-consciousness about her appearance that provokes a certain amount of face-pulling, McCartney is not so much beautiful as profoundly attractive. Phoebe, meanwhile, who was in the class below Stella at Central St Martins, is a slim, straight-talking blonde, and is walking around with a fluorescent pink piece of material tied round the waist of her T-shirt, absent-mindedly sniffing a felt-tip pen. This is a habit she�s picked up � alongside calling everyone "babe", everything "beautiful" and putting lip gloss in her hair � from Stella. Temporarily transfixed by the line-up of outfits on the wall, the two hippie chicks stand with their arms crossed, subconsciously jiggling in unison to "Smack My Bitch Up", which is pounding from the stereo.

When Kirsty Hume pokes her head around the door, Stella flings her hands in the air, crying "Cinderella�s arrived!" and plants a big kiss on her friend�s lips. Ten minutes later, Hume�s husband Donovan Leitch saunters in, promptly sits down in Stella�s office chair and puts his feet up on the desk. "But we thought you�d be playing your guitar at Jim Morrison�s grave," teases McCartney, depositing herself in his lap and then, with her ear cocked, suddenly shooting out of it. "What the hell are we listening to?" she says, pulling one of her faces. "It�s like the bloody theme to Lassie!" She changes the music for the umpteenth time today, to some obscure jungle track, cranked up so loud that the embarrassed ateliers shuffle their feet and talking becomes an impossibility. Stella admits she�s a bit of "a pain in the arse" about music, one of the oblique references she makes to being the daughter of the most famous pop star in the world. And in one way you can�t help but pity her for having had Stevie Wonder round to tea as a kid, and for having a dad who, with a personal wealth estimated in the region of �500 million, could probably buy Chlo� if he wanted to.

When I ask Monsieur Moufarrige whether that name was a positive or negative aspect when he was making the decision to hire Stella over the 41 other applicants, he tells me it wasn�t an issue because he had thought her name had been Stella McCarthy.

When I relay this to Stella she harrumphs, refusing to pass comment. The fame issue is obviously one that�s hit Stella quite hard. She�s far more reticent about her father, for example, than her father is about her. But that is nothing compared to how cagey she is about her love life. It�s common knowledge that until recently Stella had been going out with property developer Nick Milner for years. Since their break-up she has been linked with Lenny Kravitz, but when I ask her about her love life, a note of such panic-stricken urgency hits her voice I almost wish I hadn�t. "But I don�t have a boyfriend! I mean, I did have one, but not any more� look, just don�t go there, babe, OK?" And I�m afraid I never find out the reason for the knowing, kittenish smile that breaks across her face when a VIP call is put straight through to her, or when a massive bouquet of orchids and pastel roses lands on her desk while we�re talking...

Stella has never pretended she wanted to revolutionise woman�s clothing, or in fact do anything other than design clothes that she personally hankers after herself.

"It�s like some totally cool male friends of mine keep saying, �Stella, why don�t you do menswear?�" she explains. "But how could I? I�m not a man and I don�t have a dick! "I�m not really a fashion person," she continues. "What I�m about is trying to be realistic. Like, I had a lot of those stupid millennium questions � but why would I do a white number or a 2001 theme? What the next millennium is about, for me, is confidence. To me, the way forward is a totally couture sequined cape with a pair of jeans or an incredible evening gown with a denim jacket, mixing luxury with non-luxury, which is I think exactly what my parents did. In fact, it was through my mum that I found out about Chlo�. She was definitely my biggest fashion influence."

Ah, Linda. How easy it is to underestimate what an enormous influence she had on Stella. But as Barbara Daly, the make-up artist who has known the family for years, puts it, "She is completely her mother�s daughter. Her gutsiness, her set of principles, she learnt all of that from Linda� they were incredibly, incredibly close." Which makes one slightly reel back in admiration to see how well Stella is coping under the circumstances. "Well, I don�t think I really am coping," says Stella, momentarily averting that stark blue gaze as she stubs out her cigarette. "And it�s hard, very hard. My mother was such a dude, she really was. So beautiful and so real. One hundred per cent real. It�s like I�m still in denial � it�s as though she�s still here, in a way. Like, sometimes when I see a beautiful orchid, or I hear a bird singing, I think I can hear her voice." As if re-incarnated? "Oh, absolutely. That�s why I can�t understand how a person who has just been bereaved can possibly eat meat�"

The show, held at The Conservatoire, is a huge success, despite the scrum of photographers trying to get pictures of Sir Paul and Camilla Parker Bowles, and the fact that no bare bottoms are showing. Stella and her family don�t hang around afterwards. She does, however, stay to have a rant about Camilla, who had been invited as a guest of Lord Douro, the chairman of Chlo�s parent company, the Vend�me Group. Amazingly, no one had told Stella she�d be there. "I was so fucking annoyed when she came backstage, I had to lock myself away," she fairly spits. "She is not a friend of mine. Shouldn�t she be supporting a designer who�s pro-fox hunting?"

It suddenly occurs to me that walking out to all that applause as "Maybe I�m Amazed" played must have been an unspeakably emotional moment for Stella. This, after all, was the first show where Linda hadn�t been there, and though it was a success, that doesn�t mean it�s going to be entirely plain sailing from now on. But there is nothing about her freckled features to indicate anything other than a kind of steely triumph as she strides down the runway, mouth set in that defiant pout she has for the cameras. Everyone is on their feet cheering, the bank of Chlo� seamstresses at the back almost in tears with the emotion of it all. If ever there was someone who didn�t need to prove themselves any more, surely it�s Stella McCartney.