Plum Sykes waltzes into the Notting Hill café wearing an unexpected accessory. Not a controversial handbag, or last season's sunglasses, but a sling. "From signing too many copies; can you believe it?" With her crooked arm and her charcoal-grey cape perched jauntily on her shoulders, the overall effect is rather like a glamorous Napoleon (only taller). She laughs at her predicament, which couldn't have come on a worse day: tonight is her book's launch party. "I should really get a Pucci sling made for this evening."
This is pure Sykes. She is not actually going to commission a sling to match her outfit, of course. It is a camp quip, a joke at her own expense, the kind of line that makes gay male fashion designers such as Karl Lagerfeld adore her. But equally, it is the kind of comment earnest, sour types find easy to misinterpret.
Plum has a top job on American Vogue. She has a bestselling novel, Bergdorf Blondes, under her (Balenciaga) belt, and a second, The Debutante Divorcée, newly on the shelves. She has cheekbones like a Siamese cat. She has a Manhattan apartment on the same block as Jay McInerney, though she was born in London and brought up in Sevenoaks. She has a history degree from Oxford. She has a millionaire husband (Toby Rowland, son of Tiny).
She has, in fact, so many things that the British press has felt the urgent need to take as many of them away from her as possible. Her book? "Horribly empty", "a bilious swirl of superficial characters and sickly values" (reviewers also conceded, grudgingly, that as a light satire it was very funny). In 2004, an interviewer claimed that she had "ludicrous airs" and that being American Vogue editor Anna Wintour's chosen one had gone to her head. The interview was headlined "Bergdorf Bitch".
"I never get that kind of stuff in America. Never," she says as she gulps her orange juice. "A lot of things printed here are simply not true." Such as the rumour that she went to her twin sister Lucy's wedding wearing, Miss Havisham-style, the dress from her own abortive wedding, dyed black? "Yup. Don't know who made that one up."
And such as the story of her 1997 "life-altering car ride", perchance? This tale claims that a "sweet, unaffected" Plum got into a car with Anna Wintour during London Fashion Week, and got such a pep talk that she stepped out ready to take Manhattan by storm. Plum shakes her head. "So weird, that story."
What actually happened was far more prosaic, a predictable web of English upper-middle-class connections: Plum's mother, Valerie Goad, is a clothes designer, whom Wintour patronised, hence Plum and her twin sister were selected to sit for a Vogue portrait when they were debutantes, hence Wintour recognising Plum in Paris and recruiting her to New York.
"Then when I had been working for Anna for about a month I had a really awful experience," she says. "I was invited back for dinner at her house. It was a really small dinner with just Tina Brown and Harold Evans, Isabella Rossellini and her husband, and I was really intimidated. I was 27 and I had never been exposed to these kinds of people. "I was just talking to them, thinking, 'Oh, Isabella Rossellini is really nice', when Anna said, 'Why don't you lead the way downstairs for dinner, Plum?' And as I did so my shoe slipped out from underneath me and I tumbled down the stairs, head over heels, smashed the champagne glass, blood on my Chanel jacket. Everyone just stood at the top of the stairs looking down at me, horrified."
Plum beams, enjoying telling the tale of her near-social-death experience. "Then Anna said, 'Where did you get those shoes, Plum?' I said 'Prada' and she said, 'Well what do you expect with that cheap rubbish'. It was a good ice-breaker."
It is hard to imagine Plum ever being floored. Today, she seems assured beyond belief. Her posture, even on a slippery café barstool, is upright and immaculate; likewise, her mindset seems unshakably confident. For instance:
Me: "Perhaps they'll make Bergdorf Blondes for TV. It could be a great mini-series."
Plum: "A mini-series? What you want is a series. There's no point doing a mini-series."
[Later] Plum: "Here's the thing. If you're in the media, go and live in New York. It's the centre of world media."
Me: "I think most people know that but they don't have the balls to go and do it."
Plum: "But it's much easier to get a job in the media in America. Much easier than it is here. And you get paid much better."
This dauntless outlook has made Plum Sykes such a success, such a New York phenomenon. Or rather, this mental attitude combined with the talent, the looks, the contacts, the professionalism (this last is very important to her. She once ticked off Andrew Gilligan: "Take notes. Be professional"). And if there are neuroses beneath the public PMA - positive mental attitude - then they are not the obvious ones.
Despite her skeletal appearance, she doesn't have an eating disorder (a friend confirms she ate two fried eggs for breakfast every day when they went on holiday). And even when her first engagement (to the artist Damien Loeb) was broken off painfully in 2001 when she was 32, she says she never worried she would not find the right man.
"You can't think of life like that. Everyone meets someone eventually. I didn't go mad wanting children." Then she grins. "Look, have you seen Toby?" She shows me the screensaver on her phone, her smiling, dark-haired husband. "Devastating," she sighs, half-earnest, half sending herself up.
Plum is elegantly pregnant with a barely-there four-month bump. "I'm normally concave, now I'm just thin," she says. Her world is undeniably glamorous but not the vulgar, stratospherically wealthy glamour of the Park Avenue princesses she writes about. "Ridiculous," says Plum. "I'm busy writing about girls who have time to have manicures, therefore I don't have time to have manicures myself. And I take out my own rubbish."
Later, a throng of glitterati crowd Annabel's for her book launch party. It's her fourth. At the Washington one, Jenna and Lauren Bush turned up; in New York, Lindsay Lohan showed a leg. US gossip columnists drooled. In London, diarists circle like sharks. If something nasty can be said, they want to say it. All they come up with is a theory that because Plum's party is co-hosted by Matthew William-son, creative director of Pucci, Plum wearing a Pucci dress is therefore - cue sucking of teeth - highly irregular. They should have heard the plan about the Pucci arm-sling.
'The Debutante Divorcée' is out now (Fig Tree, £12.99)
A life of style: The twins who conquered New York
BORN: 1969, London. Plum and twin Lucy are the eldest of six. Christened Victoria Sykes, but called "Plum" from birth.
PARENTS: Mark Sykes (an Old Etonian roué acquainted, it is said, with Lord Lucan) and Valerie Goad (a clothes designer).
RECREATIONS: Ponies. Favourite pony is called Merrylegs.
EDUCATION: Walthamstow Hall private school, Kent. Worcester College, Oxford.
POND HOPPING: Lucy Sykes moved to New York in 1995 to work on Marie Claire; Plum followed at Anna Wintour's invitation in 1997.
BRITS ABROAD: The New York Times style supplement put the Sykeses on their cover, announcing: "They're twins. They're thin. They're attractively employed, talented. Oh and one other thing: they're English."
NOVEL ACHIEVEMENTS: Miramax paid a $600,000 (£320,000) advance for Plum's debut, Bergdorf Blondes, before she had finished writing it. But the film of the book has been held up because Bergdorf Goodman has not given its permission for Miramax to use its name. Saks Blondes, anyone?