In the Avery Fisher Hall of the Lincoln Centre on Manhattan's Upper West Side, it's four hours to showtime and there is a distinct feeling of tension in the air. Severely made-up women hiss last-minute instructions into headpieces, while an army of caterers hurriedly arranges delicate little morsels (which nobody touches) onto silver trays.

A tizzy of stylists nervously flit back and forth, their heels seemingly powered by mini jets. There are banks of altar-like make-up tables, upon which rest gigantic bouquets of white roses. This is Tommy Hilfiger's war-room and, for one night only, the rather fraught focal point of New York Fashion Week.

On a balcony above the perfumed tumult, perched on a high stool amid a cluster of lamps, sits the man himself. Lean, chicly sockless and dressed in a slim-fitting navy suit of his own design, he sighs thoughtfully at the awful significance of today's date -- September 11 -- but chooses to dwell on the positive.

"Of course I was here that day, too, and it was a terrible time for all New Yorkers," he tells me, "especially those who lost their lives, or those who lost loved ones. I was uptown, and I can clearly remember the shock and the terror. You never know when something like that is going to happen. I was living on Central Park West. I saw the second tower collapse. But today is a new day, we have a wonderful space here. And it will be a great show."

Today is also a more jarring personal anniversary in the Hilfiger calendar. It was six months ago at his spring show in New York, which took place in this very hall, that his then fiancee, Dee Ocleppo, first paraded her diamond engagement ring before the cream of New York society.

The wedding between the designer and the statuesque blonde, who had been previously linked to Prince Albert of Monaco and Bruce Willis, was to happen in two parts. Firstly there was to be a "simple" no-guests wedding on the island of Mustique, followed by a gigantic party this month at Manhattan's Plaza Hotel, at which the newly-weds would be celebrated by friends such as Harvey Weinstein, Vera Wang and Anna Wintour.

And then, without warning, in early August, the announcement came that the nuptials were off, and the couple were separating. The split was initially reported to be amicable, but the online rumour-mill had them wrangling over everything from money to honeymoon destinations.

He smiles when I bring it up, as though suddenly remembering a long-forgotten holiday that had fallen through because of inclement weather.

"Oh yes. Sure. It was just that I decided that it was awkward with so many kids in the equation [Hilfiger has four from a previous marriage, while Ocleppo has two], and that it was going to be complicated. It was both of our decisions. But you know what? We remain good friends, it was all very amicable. And, in fact, she is going to be here tonight."

As one of the few heterosexual fashion designers in the industry, Hilfiger would seem to have unique access to a bevy of lissom beauties to move on with, but he gives a rueful would-that-I-could smile at the suggestion that he would in any way use his position to his advantage.

"You know, I would say I have the pleasure of working with some very beautiful women," he begins, carefully measuring his words. "But there are certain kinds of men in their 50s who go chasing after young girls in their 20s, and I would really never want to be that kind of man."

In person, Hilfiger is cool but friendly, mildly batting away each question before moving on. He gives quick, one-sentence answers, punctuating each swiftly-made point with a beatific, close-lipped smile. He is leanly worked out, exudes a Zen calm -- the result, he tells me, of daily yoga sessions -- and, even in a room full of sleek, nattily-attired Italian publicists, his own personal style stands out.

And yet, his sartorial self-possession and sharply-cut suit seem a million miles from the breezy preppiness, and very conspicuous labelling, of his brand. Today, for obvious reasons, he's dressing up, he tells me. Most days he looks "more like you". He notes with approval my Tommy shirt ("that will never go out of style"), fingers my jacket ("is this ours too?"), but agrees that he would never do anything so vulgar as flagrantly display a logo himself.

"People wear logos because they're looking for status," he tells me. "I don't want to call attention to myself."

And you don't need status, I suggest. "Exactly."

In fact, it's been a rough few years for his brand, although it's shown strong signs of recovery recently. During the early Nineties the designer had managed the seemingly impossible, out-Ralph Lauren-ing Ralph Lauren, and selling an even cleaner, preppier Hamptons-ish glamour to the masses. For a while, every mall in America was crowded with kids wearing Hilfiger's designs. But then, in the later part of that decade, the brand strayed from the safe ground of crisp polo shirts, and into the bolder and baggier fashions of the rap world. In the short-term, this was a boon for the company and, as the likes of Snoop Dogg and Coolio were seen in Hilfiger gear, the company's share price soared to more than $40 (€27) a share.

The Hilfiger brand had reached its saturation point. With a mixture of pride and regret, the designer now tells me it was "everywhere".

But the music industry, and particularly rap stars, are fickle in their tastes and as they abandoned the red, white and blue baggies, the company turned back to its core audience only to discover the prepsters had moved on. At one point, the share price dropped to $6 (€4). In 2005, the company was sold to a private equity firm, which was charged with turning around its flagging fortunes. They developed a new line, H, which was promoted by David Bowie and Iman, but this never really took off, and there were some who questioned whether the Hilfiger name could ever be returned to its former glory. Adding to his woes was an Apprentice-style show -- in which he selected hopeful designers to work for him -- which was quickly cancelled.

Throughout, there was one sign of hope. It was noted that in Europe the Hilfiger name still enjoyed a certain level of cachet. Without a rap subculture to sully it, and his own public persona to muddy the waters, Hilfiger's brand remained at its original level of exclusivity. It was recently decided that in the US, just as in Britain and Ireland, the clothes would only be stocked in upmarket department stores and, as of this summer, Hilfiger rejected overtures from the likes of Wal-Mart, and reached an exclusive agreement with Macy's department store.

"The product in the US was broader and more mainstream, but in Europe it was more upper class," he tells me. "So we wanted to make it more like it was in Europe. And so we got rid of all the big logos, and made a collection that is today much more sophisticated and refined."

If he doesn't give the impression that the success of this strategy keeps him up at night, it may be because a lifetime in fashion has taught him that it's better to handle the inevitable ups with a degree of equanimity.

Born 57 years ago in upstate New York, Hilfiger was the eldest of nine children and remembers that this meant he had to be "a sort of a parent" to his younger brothers and sisters. "My father was a watchmaker. We were working class. I had to oversee a lot of the goings-on in the family, and so I became very responsible. I helped bring them [his siblings] up."

A slender, preppy young man, his ironic nickname at school was "the bull". "I was this big," he tells me, holding his thumb and forefinger a few inches apart: "My friend, who was big, was 'the flea,' and I was 'the bull', so that was a little joke." He was determined to play football, even if it meant getting hurt. "If you didn't, you were a wimp."

By his own account, his interest in clothing design sprang up almost from nowhere late in this sporty-preppy adolescence. At 18, he had a job in a shop selling "candles and beads, that sort of thing". With just $150 (€100) to his name, he bought a few pairs of jeans and began customising them. "I sold them to stores and they were very successful, so I decided I would start designing jeans myself. And they did well."

He would open his own store, the People's Place, in upstate New York but, with recession looming, and the local buying public diverted to a new supermall which had opened on the outskirts of the town, the People's Place went bankrupt.

Hilfiger was just 25 at that point, and decided to move to New York City with his now estranged wife, Susie, where he turned down jobs with Calvin Klein and Perry Ellis to start his own company.

"It was a wild time. I was young and starting out. I was already known in the industry and had won a number of design awards, but the wider public wouldn't have been aware of me at all," he remembers.

This was not to be the case for long. In the mid Eighties, he founded the Tommy Hilfiger Corporation, opened his own store and debuted his signature menswear collection. Slowly, a polo shirt at a time, Hilfiger began a shake-up of the fashion industry, pulling the cable-knit rug from under Ralph Lauren and Perry Ellis, while selling a sleeker, more modern preppiness to middle America. In 1992, the company went public and by the early part of this decade Hilfiger employed more than 5,000 people. His empire expanded from clothes to watches, fragrances, gloves, socks and underwear. An entire Tommy lifestyle was available for purchase.

"They were great years," he tells me. "But there were tough times too. And you have to be able to handle the low spots, especially in this industry. You have to be very humble because you can never tell when everything is going to be taken from you. Even now I think of that, even though we're on a roll. You have to brace yourself for those moments."

One such moment came a few years ago as an internet rumour spread that Hilfiger had publicly said that Latins, African-Americans, and other minorities were pulling down his brand image and really shouldn't be wearing the clothes.

"There are some things you can let slide," he tells me, "but this was something I felt I really needed to address."

He went on Oprah to publicly rubbish the claims. He says: "It was a very warm interview, and I was incredibly grateful to Oprah for giving me the opportunity to clear that up. It had gone on for years."

That Hilfiger was able to call Oprah up and ask for an audience gives an idea of his celebrity in America. The RSVP list to the show in a few hours includes Hilary Swank, and by the late afternoon there is already a smattering of photographers prowling the sidewalk outside the Lincoln Centre. Hilfiger's children, who will be in attendance, are stars in their own right now. His daughter, Ally, was featured on a sort of precursor to The Hills, MTV's Rich Girls (which, endearingly, revealed him as a bit of a doting pushover) and his son Rich Hil (the last two syllables jettisoned for coolness) is a hip-hop artist. Ally is now running her own vintage accessories business, and has said she regretted making the show. Tommy tells me that it hasn't always been a gilded passage for them.

"Certainly, my fame made things more difficult for them in a way. If you're a known person in this country, certain people will try to tear you down, that's just the way it is. You have to rise above some things."

He's said in the past that designers such as he and Ralph Lauren merely "download ideas onto people" and gives a little, bemused smile at the idea that he might do his own sewing.

"I've always been upfront about the fact that I'm a businessman and a designer. You know a lot of designers say: 'Oh all of my ideas just come out of my head', whereas I'll tell people that I'm inspired by rock 'n' roll, by photography, and by art. There's no huge secret to it."

He has a quiet day-to-day, he tells me. He lives on Park Avenue in Manhattan, and sees his children off to work before taking his yoga class -- "for fitness and relaxation". He then makes the short trip to his office in Chelsea, on the door of which there hangs a $37,000 (€25,000) pair of jeans, which were once worn by Marilyn Monroe.

"I am happy," he tells me brightly, when I wonder if this has been a tough summer.

"I feel better than I did in my 40s. I've a lot to be grateful for."

He remains on his perch after I depart, serenely watching the frenetic preparations below him. By the time I return a few hours later, a well-heeled Manhattan crowd has already mostly taken their seats in a long, multi-tiered room. The men wear brightly coloured bow ties and waistcoats, and are conspicuously sockless. The women are immaculately coiffed and wear a panoply of designers, but nothing that looks like it might have been pulled from the rack at Macy's. Nowhere, but nowhere, is the famous Tommy Hilfiger crest to be seen.

I realise that I have committed a major fashion faux pas, and discreetly pull my jacket closer to my status-hungry chest.

The sounds of George Michael singing Jesus To A Child wafts from the speakers and a bank of photographers train their lenses on the celebrities here gathered. A quiet hum of conversation gives way to a small commotion down one end of the room, as the svelte forms of Julianne Moore, Maggie Gyllenhaal and Helena Christensen take their seats. A few mortals further along sits Pharrell Williams, his earrings glinting in the evening light. In terms of magnetism, Anna Wintour, in the front row, seems to trump them all. Her huge black shades glare out like some sci-fi robot. In one swift moment the room around her shades goes black and the show begins.

The models strut down the runway, and as promised by Tommy, there is not a hoodie or rugby shirt in sight. Princess coats, sheath dresses and tunic tops over wide trousers recall the boomer years, with the palette of reds, whites and blues the only link with the brand's immediate past. It's classic Hilfiger Americana; fun, youthful, steeped in nostalgia. At the end, he emerges beaming, and walks half the runway before proffering an impish little wave to the gathered cognoscenti. Within moments, people are already filing out of the Lincoln Centre into the warm night air, forsaking the free champagne. This is New York Fashion Week and there are a lot of shows to get to.

- Donal Lynch