In France, the retirement of designer Yves Saint Laurent has been the cause of something approaching national mourning. And while the rest of the world has learned to shrug off the French obsession with chefs, chanteuses and couturiers, there is a very real sense in which the exit of Saint Laurent at the age of 65 marks the end of an era. For the French, there is a particular poignancy to his departure. Saint Laurent was the last of the great French designers. Since the late Eighties, French fashion has been in decline. The upper end of the High Street is dominated by such Americans as Donna Karan,Calvin Klein and Ralph Lauren. The trendy fashion houses are Italian: Gucci, Prada, Bottega Veneta and those veteran labels, Armani, Valentino and Versace. Even the great French houses are hiring non-French designers. Christian Dior was revived by an Englishman, John Galliano. Givenchy has seen three British designers: Galliano, Alexander McQueen and now Julien MacDonald. Chloe became a success because of Stella McCartney; her successor, Phoebe Philo, is also British. And even Chanel has had a German designer - Karl Lagerfeld - for over a decade. The saga of Saint Laurent's own house demonstrates how times are changing. Founded by Saint Laurent and his one-time lover and business manager, Pierre Berge, in the Sixties, the house never made any money from the couture that made Saint Laurent famous. It made its money from the fame. In the late Sixties, in an unusually prescient gesture, Berge and Saint Laurent decided that couture was finished and that the future of fashion lay in ready-to-wear. Accordingly, they set up a chain of boutiques called Rive Gauche, selling factory-made clothes that bore the Saint Laurent name even though the master himself had not designed them. They followed up the success of the boutiques with the growth of a huge perfume empire boasting such famous names as Opium (considered daring during its Seventies launch), Rive Gauche (what we would now call a brand tie-in) and Paris. Saint Laurent had nothing to do with the perfumes which were devised by professional perfume houses under instructions from Berge and his team. But by the Seventies, he was the most famous designer in the world and his name sold the perfumes. All went well till the Eighties when the Americans and the Italians began to dominate the fashion business. Though Saint Laurent was still acknowledged as the world's most influential designer of haute couture, the house itself lost its way. Berge failed to develop the Rive Gauche concept as he should have in the age of ready-to-wear. The perfume business stagnated; the old brands did well but there were not enough new successes to ensure growth. While the house was taking the wrong turns, the notoriously fragile Saint Laurent was lurching from emotional breakdown to nervous collapse, fuelled by addiction to drugs and tranquillizers. He would disappear to his house in Marrakesh for months on end. He would not emerge from bed for days. He wouldn't turn up at his own shows. And he would tell friends that he wanted to give it all up. While his creative genius was undeniable, his influence on trends became less noticeable. He had made his name with the Trapeze collection in 1958, his first for Dior, and invented such staples of the fashion business as the Mondrian print (after the style of the painter). His 'Le Smoking', the tuxedo for women, was inaugurated in 1966, as was the sheer blouse, both of which went on to become fashion classics. In 1968 came the jumpsuit, and in 1976 the Ballet Russes collection, whose Russian influence lingered on the High Street for years. But while Saint Laurent was the first designer to give women the convenience and freedom of men's clothes, his early innovations were followed by a creative lull. Meanwhile, Berge cheapened the YSL brand by licensing the name to manufacturers of bath towels and key chains. In America, large conglomerates produced YSL suits that would have made the couturier throw up if he had ever seen them. Consequently, by the Nineties, the decline of YSL as a fashion brand paralleled the designer's decline into depression. Berge had seen the writing on the wall, selling off part of the beauty business (which owned the perfumes). In 1993, the empire was acquired by the French conglomerate, Elf-Sanofi. Then in 1999, Sanofi sold out to Artemis, owned by Francois Pinault, the millionaire investor who owns a chunk of the Gucci group. Pinault transferred his holdings to Gucci, entrusting the YSL brand to the Italian fashion house's CEO, Dominic De Sole, and its hot, young designer, the American Tom Ford. As part of the deal, Pinault allowed Berge and Saint Laurent control of the couture house, but they surrendered all control of the perfume business and - most significant of all - of the YSL Rive Gauche ready-to-wear label. Ford soon evicted the American designer, Alber Elbaz, whom Saint Laurent had hired for ready-to-wear, and appointed himself chief designer (Saint Laurent's menswear designer, Hedi Slimane, had already walked out to join Dior). De Sole cancelled most of the licenses the greedy Berge had awarded and concentrated on taking the house upmarket. And so began the greatest confusion in fashion. Soon, there were two YSLs. There was the couture, the basis of any great label, designed by Saint Laurent himself. And there was a very different ready-to-wear collection which reflected Ford's flashier, more Italian-influenced style. At first, Ford tried to pay homage to the master. At his first menswear collection, he made the models wear Saint Laurent's trademark glasses. Each of his womenswear collections contained take-offs on the classic Saint Laurent tuxedo. And he told interviewers that Saint Laurent was his idol. Unfortunately, Saint Laurent hated Ford's clothes. (This is not as big a deal as it sounds. He also hates Ralph Lauren - whom he famously, and successfully, sued for ripping off his Le Smoking - together with John Galliano, Jean Paul Gaultier and nearly everybody else you can think of.) He refused to show up at any of the fashion shows, though he was in the front row at Hedi Slimane's debut show for Dior. And Saint Laurent's acolytes helpfully offered that he thought that Ford's style was vulgar. The contrast between the two men could not have been greater. Saint Laurent thinks of himself as an artist, has a tortured sensibility and spent his youth traumatized by his homosexuality before finally coming out in an interview. Ford is a former model, does not call himself an artist, is outstandingly commercial, prides himself on being market-savvy and is proud to be gay. When his YSL collections became huge successes, while Saint Laurent's couture collections had minimal impact, the trend was clear. The era of the artist was over. The market-savvy craftsman had won. Even so, it is not clear why Saint Laurent suddenly decided to call it a day. The charitable view is that he tired of creating timeless couture for an ungrateful world that preferred flashier ready-to-wear. A less charitable theory is that he decided to throw in the towel because he had lost. YSL is once again the hottest label in the shops - but it is Tom Ford's YSL, not Saint Laurent's. Either way, Saint Laurent is not taking any chances with the couture label. After he shows his last collection on January 23, 2002, at the Pompidou Centre in Paris, the house will not go to Ford, nor will it hire another designer. It will retire with Yves Saint Laurent.