Ainsley takes Manhattan!

(or, as they're saying in New York: 'Thank you, England, for sending us the big bald bloke from Balham')

It is 8.55am, a time of day not normally associated with mass frenzy. But this is New York. To be precise, this is television studio F at Chelsea Piers in lower Manhattan, just across the Hudson River from Hoboken, New Jersey, birthplace of Francis Albert Sinatra. And Al Rosenberg, the roly-poly warm-up man, has whipped the audience into a tumult of anticipation that Sinatra would have recognised. "Now," he shouts, "I want you to give a greeting to the man himself. What I want to hear from you is the love I know you feel for him. Are you ready? ARE YOU READY?" The audience shrieks its readiness. "OK. Then put your hands together ... for ... AINSLEY HARRIOTT!"

Behind me, Maxine Tishman, a plump, middle-aged travel agent from Staten Island, leaps to her feet, clapping and cheering. This is her third time in the audience of NBC's The Ainsley Harriott Show, and her face is flushed with delight, as is that of her friend Nancy Sloman. The object of their adoration, wearing a pink shirt under an even pinker tank-top, gyrates into view. At which point another woman, old enough to know better, actually screams.

This is Ainsleymania, New York's phenomenon of the moment. And it is not confined to the over-forties; alongside me is a group of whooping high-school girls. Nor is it confined to women. All the same, Ainsleymania, like Beatlemania, has a distinctly sexual edge. Ainsley's pepper mill - which he innocently christened "Percy Pepper" on the BBC series Can't Cook, Won't Cook - has become an American phallic symbol. Later, when Maxine Tishman has recovered some poise, she tells me coquettishly: "That Percy Pepper is enough to get any female going."

Bizarrely, there are plans afoot to turn Percy Pepper, his playmate Suzy Salt, and Harriott himself, into television cartoon characters.

America has evidently gone mad. Mad for a bald, black, 43-year-old Englishman, whose principal place of residence is with his wife and two children in unfashionable Balham, south London, yet whose grinning face now adorns the sides of dozens of New York City buses. Who as recently as 1994 was a little-known chef at Lord's cricket ground, where he had worked for 19 years, yet who three weeks ago had merely to take his place in the audience at an off-Broadway theatre to receive a standing ovation from those around him.

So what happened? Last Thursday morning, Carlotta Lucas assured me that without Ainsley her life would be bereft. Carlotta is a working-class grandmother from the Bronx. Just three months ago, for heaven's sake, she had never heard of him.

In Britain, Harriott's rise to television stardom was plodding rather than precipitous. For years he combined his cooking career with a parallel existence on the alternative cabaret circuit as half of a comedy duo called the Calypso Twins. It was a BBC radio producer who finally spotted that there was a rich concoction to be made out of his charisma, his rapport with an audience, and his flair in the kitchen, which had been handed down from his maternal grandfather, Clifford T Strudwick, a celebrated Jamaican chef whose main claim to fame was that he once cooked for President Franklin D Roosevelt.

Harriott duly became the presenter of Radio 5's More Nosh, Less Dosh. A telly career followed. He became a fixture on Ready Steady Cook and Can't Cook, Won't Cook. He acquired first-name status, with Ainsley's Barbecue Bible and Ainsley's Big Cook-Out. He was warm, engaging, and Middle England mostly loved him. But he also had his critics. He was, after all, the antithesis of the blessed Delia. The gregariousness, the basso-profondo laugh, the jiggling and jiving, even the recipes, were not to everybody's taste.

Merv Griffin, however, thought he was sensational. From 1963 to 1986, The Merv Griffin Show was an American television institution. But Griffin was more than a mere talk-show host. He built up a vast business empire which extended from television production to luxury hotel management. And in early 1998, while visiting one of his hotels in Ireland, he was in the bathroom shaving when a friend, captivated by an unfamiliar spectacle on television, called him through to take a look. It was Can't Cook, Won't Cook, featuring Ainsley Harriott at his most extrovert. Lathered in shaving foam, Griffin wandered out of the bathroom. Twenty minutes later the foam had dried on his face. "I was mesmerised," he later recalled. "I couldn't take my eyes off him. I called the LA office and said 'you've got to find out who this guy is ... America would go crazy over him.'"

It took two years for him to be proved right. A couple of pilot shows were made. NBC dithered. But eventually, Harriott's agent phoned him in Balham to say that the network had flashed the green light. "I said 'Oh, that's good'," recalls Harriott. "Then I put the phone down and went 'Waaagggghhh!'" Not many British television stars have succeeded in America. Tracey Ullman has, as have the Teletubbies, but plenty have failed. Still, at least Harriott was getting a shot.

Gradually, the show's format took shape. It would be a chat show with cookery rather than a cookery show with chat. He didn't want a sidekick but he did want a live band. He got his way. "But then it was 'what sort of band?' We must have seen 20, from all-women bands to bands that couldn't play a note. I'd say 'what type of sound would you play if I was grating some cheese?' and they'd go into some big Latino number." He gives his trademark roar of laughter. "It was crazy."

We are sitting in Harriott's plush office backstage at studio F, between his live morning show and his taped afternoon show. He has just been interviewed by a woman from People magazine. He has already been profiled by the mass-circulation USA Today. In the street, passers-by yell his catchphrase at him: "Hey Ainsley," they shout. "What are you like?"

In the last two months, the name Ainsley has even started to appear on American birth certificates. Yet Ainsley Harriott wears his burgeoning fame, as he wears his pink tank-top, without any discernible self-consciousness. And he is clearly adored by his colleagues, many of whom are used to presenters who behave like prima donnas. All the same, the warm-up man, Al Rosenberg, perhaps slightly overcooks the praise, assuring me, "There is nobody here who wouldn't take a bullet for Ainsley. God bless England for sending him."

Minutes later, Al Rosenberg is back in action, as another audience files into studio F. It includes Carlotta Lucas, making the three-hour round trip from the Bronx for the 10th time. "I look at him every blessed day," she tells me. "I love his accent, I love him and I love his recipes. I've done his meatloaf, his macaroni cheese, his potato fish sticks and his sweet potato gnocchi." Today she will learn how to cook grilled salmon with cranberry rice.

Harriott has had to develop a new repertoire of dishes to suit American tastes, not to mention a new vocabulary. Courgettes and coriander mean nothing to Americans familiar with zucchini and cilantro. But he is careful to pepper his show with plenty of phrases from the old country. To my delight, there is actually a smattering of applause when he says: "I'll just pop a bit of wine in there."

Then his celebrity guest, a New York DJ called Jay Thomas, asks him why he flamboyantly tosses the contents of his pans rather than stirring them with a spoon. "Jay," he says, "there are some people in life who are stirrers and some who are tossers." In America these words carry no double entendre. I chortle alone while everyone else nods, solemnly digesting one of Ainsley's great philosophical truths. Later, with a huge guffaw, he somewhat ambiguously tells me that it was a line intended just for me.

Since The Ainsley Harriott Show started on 10 January, the guests have increasingly come from the celebrity A-list, a pretty reliable indication of success in American television. Danny De Vito, Joan Rivers and Evander Holyfield have been on. So have Richard Branson and the Duchess of York. Significantly, on three successive days the week before last, the show got better ratings than ABC's long-established Rosie O'Donnell Show.

But that was only in New York. Percy Pepper has yet to seduce Middle America, and NBC executives have yet to decide whether to give The Ainsley Harriott Show another season. Stacey Agdern, a law student from Albany, New York, in the audience for the first time but a committed fan, thinks it inconceivable that they won't. "America needs Ainsley," she says, and she ain't kidding.