It is reassuring to discover that, even at the most elevated social gatherings, the question of small talk is still troublesome. In the foyer of the Metropolitan Museum of Art, on a warm spring night in New York, Drew Barrymore, Gisele Bündchen and Charlize Theron mill stiffly about in the early stages of a party, trying to find their groove. "I'm five foot 11," says Bündchen, stretching her neck.
"I'm five foot two!" says Barrymore. Theron declines to state her height, but looks gravely into the middle distance and swishes her ballgown like a crocodile straightening its tail. There is no obvious follow-up to the how-tall-are-you ice-breaker and the three women lapse into an awkward silence, which is relieved only by the sound of Kate Moss, several feet away, telling Vivienne Westwood a story about some jeans ("... said they didn't work with the shirt, but I tell you what, they fackin' did").
This is the launch party for Anglomania, the museum's annual costume exhibition which this year is devoted to the history of British fashion. Small talk shouldn't matter since the hostess, famously, doesn't indulge in it. At half past six, Anna Wintour shoots through the lobby, eyes fixed forward, to take her place alongside co-hosts Sienna Miller (chosen, says Wintour, because she represents the "best of British style"), Rose Marie Bravo (the head of Burberry, which is sponsoring the event) and, for some reason I never get to the bottom of, the Duke of Devonshire. Together, they form a receiving line, past which troop Oscar winners, Grammy winners, Emmy winners, It girls, billionaires, heiresses, a flock of supermodels and the occasional high-functioning "civilian", as Liz Hurley, also present, might put it, such as the woman in grey chiffon who enters the room, takes one look and croaks, "I need a drink." I spot Baroness Amos, leader of the House of Lords, and strike out for her, but I am floored by a woman hissing to her silver-haired escort, "Stop fussing, Manolo!" Manolo Blahnik stops fussing and, as the sun fades on the museum's limestone exterior, humbly takes his place in line to greet Wintour.
Anna Wintour is the editor of American Vogue, but this doesn't begin to explain it. Although at 56 she has edited the title for the past 18 years, she stopped being regarded as a journalist long ago and became, instead, a sort of proxy for the entire fashion industry. In conversations I have with friends before meeting her, she is variously imagined to be brilliant, stupid, an artist, a bully, a hero, a scapegoat, an empowerer and the reason why women get eating disorders. The fact that she is imagined to be anything at all is a sign of her reach, and although she claims not to be aware of her iconic status, she constantly - some might say fanatically - reinforces it. (If she is tired of people commenting on her Chanel sunglasses, it is not enough to stop her wearing them.) The only thing everyone can agree upon is that she is above fashion because she is fashion. She is also British which, given the care she takes over her appearance, is one of the most unfathomable things about her.
"I don't want you to get the wrong idea," she says. This is four days before the party and we are in Wintour's office at Vogue, in Times Square. She is standing by her desk, sheathed in white. "I'm not the curator, I'm the facilitator. I help with the sponsorship [of Anglomania] and putting the party together. I'm in the background." She smiles.
It can't be terribly relaxing for Wintour, meeting new people. If she is awkward, it is partly a reflection of how awkward people are with her, particularly women, who get pre-emptively chippy when faced with the prospect of meeting Fashion Incarnate. Wintour's manner doesn't do much to alleviate this; she speaks in a bored tone, as if on sufferance, although she has always said she is shy, not aloof. A lot of what is written about her is unfair. She has been snidely labelled a "man's woman", while being slated for things male editors are not. So, while her management style is notoriously imperial - there are all sorts of rumours about staff etiquette at Vogue - it is no wackier than anywhere else in the Condé Nast publishing empire, certainly not Vanity Fair, for which Graydon Carter doesn't get anything like the same kind of stick.
And she is a good editor. As well as the fashion spreads, recent issues have run pieces by Joyce Carol Oates and Edmund White, an interview with the new president of Chile, Michelle Bachelet, and a political piece by Donna Tartt. A former employee of Wintour's at British Vogue remembers her, if not exactly warmly, then with respect, as someone who worked hard and had an eye for detail. Wintour is fond of saying, "If you look at any great fashion photograph out of context, it will tell you just as much about what's going on in the world as a headline in the New York Times." At the moment, therefore, she says, "the clothes this season are very militant and urban, and have a sense of going into battle". Not the most searing critique of world affairs, perhaps, but you take her point.
When I ask if she is trying to make the magazine more political, however, she looks at me as if I've asked to set fire to her office; like the Queen, she doesn't dirty the hands with actual opinions. She does, however, make a passionate speech about how wrong it is for politicians to patronise the fashion world.
"Washington is frightened of fashion. I think the British government has the same ... People in political office tend to get extremely nervous about fashion because they feel it's frivolous. And they don't want to look too elitist or too silly or whatever it may be. And, frankly, it makes me extremely angry, because it's such a huge industry for Britain and for every country, and I feel that politicians should embrace it, rather than step away from it. And I wish the British government would get more involved in fashion and turn up at some of the shows or have people to Downing Street. I know that Blair did that at the beginning and, I think, got criticised for having some people there who weren't considered serious, and I feel that is so insulting to the industry, because it does so much for Britain. There are all these huge talents coming out of the country; they ought to be celebrating it."
Drumming up publicity for Anglomania is Wintour's contribution to the cause. Her enthusiasm for British designers - in this case Vivienne Westwood, John Galliano, Stella McCartney - and the relationship between designers and the fashion press generally is regarded, by the non-fashion press, as evidence of a resident evil: that their sympathies lie with advertisers more than readers. Wintour won't be bullied, as her dealings with the anti-fur activists have shown, and there's a story that goes around about how, when the Armani company suggested they might reconsider their advertising spend with the big fashion magazines unless their clothes were used more liberally on the pages, the only editor to tell them to naff off was Wintour. You're a hero, I say.
She smiles tightly. "Oh, right."
"It's a great story."
"Mmm, well, it's water under the bridge."
"You were the only one who stood up to them."
No answer.
"And they crumbled."
The smile fixes.
"Did it give you satisfaction to have won?"
"Well, I'm happy that Giorgio is coming to the exhibition on Monday morning. So. That was all a long time ago."
A lot of discussion goes into who, exactly, has the goods to make it as a Vogue cover girl; Wintour uses words such as "sophisticated", "quirky", "interesting" and "intelligent" to describe the Vogue look. It was too late to replace a perky-looking Britney Spears on the first post-9/11 issue, so they draped an American flag behind her and hoped it would do. Keira Knightley is on the cover of this month's issue. "Her Elizabeth Bennet was brilliant; that's a really hard role for a young girl to take on when it's been done so many times. She's someone who interests Vogue." Jennifer Aniston was on last month's cover. "Very much the girl next door and doesn't think of herself as a fashion girl," says Wintour.
It makes sense that the "girls" who work at Vogue must be well turned out, although you wonder where the cut-off is. Bitten nails? Split ends? Last season's colours? As for the people appearing in the magazine, Wintour says there is no rule about whether, for example, case studies in a non-fashion-related story must be photogenic, although, "we want an attractive presence". So can unattractive people make it into Vogue? Wintour turns to look out of the window and sighs, irritably. "I'll have Patrick [Vogue communications director] show you a couple of pictures." She picks up the phone. "Yuh, hi. Can you have Patrick O'Connell pull out the pictures of the obesity story we did, please? Thank you."
At the party there is the usual elephant in the room - this being that, with one or two exceptions, there isn't a woman present who doesn't look as if she's hosting a tapeworm. I ask Wintour if the fashion industry contrives to make women feel bad about themselves. She looks thoroughly martyred. "I think that's nonsense. It wants to celebrate women. And I think one of the things that's happening in fashion today is that there's so much more fashion available at so many different price levels. I think women look better than they've ever looked. And if a woman feels bad about herself, then there's something more seriously wrong with that woman than the fashion industry." When I leave the interview, there are photocopies of the obesity feature ready for me.
At some stage in her career, Anna Wintour stopped being Anna Wintour and became "Anna Wintour", at which point, like wings of a stately home, she closed off large sections of her personality to the public. The last relaxed interview she seems to have given was in 1986, to the Guardian, on the occasion of being made editor of British Vogue. That was her big break. She had grown up in London, the daughter of Charles Wintour, editor of the Evening Standard, and his American wife, Elinor, a philanthropist. After stints in New York at Harper's Bazaar and a short-lived title called Viva, one of Bob Guccione's, Wintour returned to London at the age of 36, while her husband, David Shaffer, stayed on in New York.
"The logistics are terrible," she told the journalist, Linda Blandford, at the time. "I wake up at night in a cold sweat. Endlessly, parts of one think, 'I'm crazy. I should stay home, look after my baby, have a nice quiet life.' But I didn't think I wanted to have a kid in New York. I've worked so hard for 15 years here - and British Vogue was always the magazine I wanted to edit. Will it work? Ask me in six months."
Evidently it did work and in 1988 she returned, all-conquering, to New York to take up the post of editor-in-chief of American Vogue. It is hard to imagine Wintour speaking so freely about her vulnerabilities now. She talks proudly of the daughter she has at Columbia University and the son at Oxford, but clams up on anything personal other than that. In that same 1986 interview, she said, "In the face of my brothers' and sister's academic success, I felt I was rather a failure. They were superbright so I guess I worked at being decorative. Most of the time, I was hiding behind my hair and I was paralytically shy. I've always been a joke in my family. They've always thought I am deeply unserious."
Now she says, "Well, I had a lot of fun in London when I was growing up, and I think the most important thing was that my mother worked, and I think that was quite unusual at that time. Both my parents taught me a great work ethic."
The work ethic is one thing. But the getting up at dawn for hair and make-up is something else. At British Vogue, current editor Alexandra Shulman cheerfully admits that the spotless "Vogue look" isn't always attainable, even by her. Wintour's unwavering ability to look as if she lives within the pages of her magazine has a sort of honesty to it, proof that, whatever one thinks about it, the lifestyle peddled by Vogue is at least physically possible.
It is on the subject of Englishness that Wintour is most human; her magazine bangs a drum for British culture in a way that, if you didn't know better, you might suspect grew out of nostalgia. The April issue featured items on Jordan, the TV show Little Britain, Alan Bennett and the UK rap scene. The young, English designers Wintour favours at the moment are Basso & Brooke, Luella Bartley, Hussein Chalayan, Stella McCartney, Phoebe Philo. "I've always been a great fan of British fashion. I think that they have so much originality and personality, and are not worried about being commercial the way people are sometimes in the States."
She enthuses about Sienna Miller. "I'm thrilled that Sienna is doing this [co-hosting Anglomania] because, to me, she represents the best of British style. When we were working with her on her dress, just the way that she put it together and thought about accessories and how she wanted to break the mould ... I think sometimes American girls are more streamlined and more perfect. But for this exhibition we want a quirky and eccentric and individual [look] in a way that British fashion is. It's more athletic over here. It's more polished. It's ..." she smiles, "healthier."
Wintour's own style is famously unchanging. I ask what she thought of Edna Mode, the cartoon character in the Incredibles, apparently based on her, who advised style-conscious superheroes against the wisdom of wearing capes.
"I didn't see it. Sorry."
Does she think sexism has influenced the way she is written about? "I just don't think about it really. I just try to do my job the best that I can. I've kind of learned not to even pay any attention. So, whether it's sexism or whatever, I think you just have to feel good about what you're doing, and the people you're working with, the different initiatives we do: our Aids initiative, the Met... these are all things that mean a lot to me. That's far more important than what some tabloid newspaper might be writing."
The tabloids have had rich pickings lately, with the breakdown of her marriage to the child psychologist Shaffer and subsequent relationship with J Shelby Bryan, a former cellphone millionaire. They met 10 years ago at a dinner party. An insider at Condé Nast, who knows both of them, says, "The attraction to her is that he came courting. He's a seducer and a salesman, one of those guys who can promise you the world. He's actually quite impressive."
Behind the armour of Wintour's public image, it's impossible to imagine what she is like off-duty. She has no apparent sense of humour - certainly no sense of the ridiculous, although you occasionally wonder when you see pictures of her wearing a big fur coat, out of which her head protrudes, like someone surfacing through a manhole.
And so to the party. In the minutes before the doors open, functionaries from Vogue flit about, whispering viciously. "Have you seen Marsha or the girls from Burberry? David? Is that where you're going to stand? David!" The index of fame to desperation is measured by how long each guest spends on the red carpet relative to the amount of noise the photographers make at them. Naomi Campbell gets the biggest roar for the least amount of posing time. (The only other person to skip the receiving line so flagrantly is Rupert Murdoch.) At one point, Jennifer Lopez walks in. The queue to meet Wintour is quite long and Lopez frowns, not sure of what to make of it. "You guys?" she says. "You guys?" A note of panic enters her voice. "OK, what's happening?"
When I get back to London, I ring Baroness Amos. She was there representing the government, in an Amanda Wakeley dress and Jimmy Choo shoes. She met Stella McCartney and Johnny Rotten. But it was Wintour she was interested in. "Just from everything I've read, I really wanted to meet her," she says. "There are so many stories about her being energetic and dynamic, and also a bit of me just wanted to meet someone who is British and hugely successful in the United States." They chatted, briefly, about the need for government support of British fashion. And? Baroness Amos says, "She was very warm."
After her entrance, I don't see Wintour for the rest of the party. The last exchange I have with her is the afternoon after the interview, when I see her at the museum. She is taking a last look around the exhibits, which feature, among other things, a suit by Stella McCartney, lots of Vivienne Westwood punk, the Duchess of Cornwall's wedding hat and a tableau that creates a "dialogue", as curators put it, between Queen Victoria's mourning weeds and the dress Gwyneth Paltrow wore to the Oscars. It is bonkers, but fun and revealing of the way British fashion has plundered its own past. Wintour stalks through the dimly lit rooms in her shades while I speak to the curator. Suddenly, she charges over. "Do you have everything you need?" she asks, but before I can finish answering, she has turned on her heel and walked briskly away.