Not content with rewriting the rules of British cooking, Ruth Rogers and Rose Gray - whose latest cookbook is about to hit the shelves - have spawned an entire generation of chic chefs: the Children of the River Cafe

The River Cafe phenomenon rolls on. Like Old Testament prophets expounding their creed, the River Cafe cooks prepare to launch yet another, the fourth, of their cookbooks, inspirational texts addressed to an ever-increasing band of followers.

The new one, published next month, is appropriately called The River Cafe Green Cookbook, a title which encapsulates their ecological fervour and organic mission. For River Cafe cooking is a way of thinking as much as a way of eating.

Only a dozen years after they opened their seminal restaurant in Hammersmith (featuring cucina rustica, the home cooking of Tuscany, as its inspiration) it becomes clear that the owner-cooks, Ruth Rogers and Rose Gray, are responsible for a sea change in the British approach to eating.

Did they not light the blue paper which led to the explosion of sun-dried tomatoes? Did they not make the peasant foods of Italy, polenta and bruschetta, fashionable in top London society? Did they not raise expectations in our olive oils?

Hardly a restaurant in London doesn't owe something to them. And not only restaurants, supermarkets too. Marks & Spencer have launched a new range of Italian dishes this month which are ambitious in a way that would have been inconceivable a decade ago, ready-to-go boxes of lasagne with spinach and Parmesan, borlotti beans and salads of mustardy rocket leaves.

But while Ruth and Rose continue to publish the tenets of this new food religion, we are also beginning to see the works of their disciples. The Children of the River Cafe are beginning to make waves. Hugh Fearnley-Whittingstall, with no fewer than nine entertaining TV food series under his belt, was the first of the River Cafe graduates to hit the big-time. He remembers the very earliest years, in the 1980s.

"It was very exciting. Even then you knew you were part of something very special." A friend who was a waitress there had recommended him. "I went to see Ruthie and Rose and they put an apron on me and I started preparing the vegetables. In the afternoon they said, 'What do you like to cook?' and I said, 'Desserts.' 'Oh, good,' they said, 'no one seems to like making puddings.' I made a lemon tart and they said, 'Come back tomorrow.'"

It was about the time that stories about Marco Pierre White were circulating, he says. "The idea was that you had to have blood, sweat and tears to succeed. It clearly wasn't true. I learnt a fantastic amount. What they did was so simple but they set new standards of cooking and style."

Fearnley-Whittingstall was actually the first and last employee to have been sacked at the River Cafe - having filled the kitchen with a mess of chocolate. One can only imagine the scene. He bears no grudge. "I can't prepare a squid or bone a leg of lamb without thinking happily of them."

The River Cafe's most famous son has to be Jamie Oliver, whose debut TV series last year was a staggering success. On the back of it, his first book soared to the top of the non-fiction list (elbowing out Delia Smith in the process) and has stayed there for six months.

Jamie is a Robbie Williams of the cooking world, a charismatic and youthful lad who translates Rose and Ruthie's interpretations of Italian dishes into Estuary English. But he allows no compromise: he orders you to use nothing but the most "pukka" extra virgin olive oil.

Jamie is already the ultimate TV celebrity cook of the day, in demand for lucrative public appearances and sponsorships and to put his name to cookery columns. There's talk of him opening his own restaurant in Cambridge. And for his next book, due out later this year, his agent is apparently seeking a six-figure serialisation fee.

None of his erstwhile colleagues begrudge him his success. Many of them are making waves themselves, opening restaurants of their own. Of the older Children of the River Cafe, the most renowned and acclaimed are the two Sam Clarks, the young husband and wife team who run Moro. After only two years it has won acclaim for doing for Spanish and North African food exactly what the River Cafe did for Italian dishes, redefining and popularising them.

Husband Sam worked at the River Cafe for five years before his wife did an 18-month stint. "I can't think of a better place to train," she says. "Their whole approach sets you up. It's an attitude to food, a style, a respect for ingredients, integrity." A Moro cookbook is to be published next year.

A few weeks ago, another Child of the River Cafe, Allegra McEvedy, published her first book, The Good Cook (see recipe overleaf). This personable 28-year-old trained at the River Cafe before moving to New York to cook for Robert de Niro's fashionable TriBeCa Grill. She became "sick of cooking for posh people" and returned to London to set up a low-priced café, the Good Cook, in the Tabernacle, a community centre off Portobello Road. At two courses for a fiver, with side orders at £1.50, it has been the best food value in town. Next month she relocates to No 1 Kensington High Street, and a television series may not be far off.

In another part of west London, ex-River Cafe cook Celia Harvey has taken over a pub, Golborne House, and intends to steer it up the River Cafe path. A New Zealander, she'd planned to train in the UK and return home, but changed her mind after three and a half years with Ruth and Rose. "I loved every minute," she recalls. "It's like being in a large family. It's a fabulous place to work."

Another River Cafe cook was Darren Simpson, one of the first graduates of the restaurant to get a high-profile job, opening Sir Terence Conran's Italian-style Sartoria in Savile Row.

There have been other River Cafe graduates, notably Mark Nathan who had the vegetarian Museum Street Café before moving to the south of France. And Francesca Melman who opened The Vale in Maida Vale, eight months ago, a converted pub serving Modern British food. She'd had two years professional experience, at the Brackenbury in Hammersmith, before joining the River Cafe. "I thought it was a terrible joke at first, and wondered, why am I working with these two mad ladies? And then I noticed, all the best chefs were coming here to eat. There must be something about it. It was very difficult at first, I had to relearn everything. The real lesson was to learn how to leave things alone."

It's been a very subtle and very gentle revolution, this anglicisation of Italian food. And it all goes back to a common denominator, Dada, mother of Lord Rogers, the architect.

Rose, a friend of Lord Rogers's first wife Sue, met her in Florence, part of a love affair with Italy which blossomed when she went to live in Tuscany with her husband, artist David MacIlwaine, planning to write a book on pasta.

Ruth, living with her husband in Paris in the 1970s (he designed the Pompidou Centre) met her mother-in-law in Florence and was immediately converted from French cuisine to cucina rustica.

"I remember tasting for the first time those wonderful rustic dishes," Ruth recalled. "Bread soups and bean soups, pasta and polenta, proper pomodoro. In Paris a piece of fish was masked and disguised. Here food was simple, clean and pure. Once I had eaten home Italian cooking, I didn't want to eat anything else."

Neither Ruth nor Rose had had real Italian food before. Ruth, who came from upstate New York, had childhood memories of spaghetti and meatballs with tomato sauce. Rose had grim memories of London restaurants. "There was always boiled artichoke served cold, cold fish salads, chicken Kiev - dishes I have never come across in Italy."

When they opened the River Cafe in 1987 it served as a canteen for Lord Rogers's architectural practice, tucked away behind a maze of streets off the Fulham Palace Road. It didn't remain hidden long. Chef Simon Hopkinson confidently invited the fussy Elizabeth David as his guest, Fay Maschler, the top critic gave it the seal of approval, and in no time at all the New Yorker was hailing it the best Italian restaurant in Europe, Italy included.

Hollywood producers and actors soon booked into this desirable destination, mixing with not only the top European architects but the select literati and glitterati of London: Sir David Puttnam, Lord Palumbo, Bob Hoskins, Kenneth Branagh, Lucien Freud, John Mortimer, Martin Amis, Mick Jagger, etc. All passionate customers.

They can be sure of a rare welcome because, unlike many British restaurants, the meeting and greeting is on another plane. It was no accident that Ruth and Rose decided to match Italian standards of food with American-style service, with smartly dressed, good-looking young staff who know what they are doing and obviously like it.

But, as Hugh Fernley-Whittingstall emphasises: "There have been many factors in the River Cafe's success, but the strongest factor has been the food."