Prepare to feel very, very sorry indeed for Naomi Campbell. This week the poor lamb announced she was scaling down her career, citing excessive stress as her primary reason. "I find it really stressful doing 16 shows and then having to do fittings and dress rehearsals," said a fatigued Miss Campbell to a largely unsympathetic press.

But who would blame her for feeling the way she does, especially after spending half her life in the same business? Modelling can be hard work, although an estimated annual income in the region of £1 million presumably permits Miss Campbell to afford a few anti-stress treatments. Still, her imminent departure from the international catwalks should be mourned for another reason because she represents the last of that now-vanished breed, the supermodel.

Once held in high esteem, the sobriquet supermodel today sounds just so dated and, really, so hopelessly "nineties" - and in fashion, a more crushing epithet than that is unimaginable. That the supermodels belong to another age is easily proved by comparing the global fame enjoyed by Naomi, Cindy, Linda and Christy (all easily remembered two-syllable names) with what their successors can hope to achieve.

The most successful model de nos jours is a 19-year old Brazilian called Giselle Bundchen who last month was simultaneously on the covers of British and American Vogue and of Harper's Bazaar.

Vanity Fair has written of Giselle's attributes, as has W magazine, while in New York in December she was pronounced the Vogue/ VH1 Model of the Year. Paeans of praise have been lavished on her curvaceous body, her 36-inch chest, her pouting lips and glistening skin.

Within the fashion industry, this girlwoman is perceived as perfection incarnate, but outside it, who has ever heard of her? Who knows about Karen Elson (the "Face of 1997"), Erin O'Connor, Maggie Rizer, Carolyn Murphy or even Amber Valletta?

The last of these, top-selling cover girl of American Vogue in 1998, has probably been the most commercially successful model for the past five years. But that does not necessarily mean the general public is familiar with her name or wishes to know any details of her personal life. Outside her profession, Miss Valletta is entirely anonymous.

Were she, rather than Claudia Schiffer, to have recently become engaged to British socialite Tim Jeffries, it is unlikely the event would have excited much tabloid interest. Amber Valletta could give birth to octuplets and this occurrence would not be considered as newsworthy as the one child produced by Cindy Crawford.

Today's crop of models may be every bit as lovely as their professional forbears, but they are not nearly as well known.

The models themselves may, of course, be very happy with this state of affairs. Fame, as Naomi and her peers can testify, is indisputably a mixed blessing. When the supermodel concept first emerged, it must have seemed rather amusing. Here, after all, were a group of women who had achieved notoriety simply for being seen wearing clothes designed by other people.

Nothing else was required of them. Here, seemingly, was an impeccable instance of fame existing for its own sake. In fact, the supermodel phenomenon emerged as one part of fashion's shift from being a minority interest to representing a branch of the mass-market entertainment industry.

That fashion today has very little interest in clothing is a commonplace within the industry. Creativity and imagination in design have not been much seen for the past 10 years, but the global business has grown so big that it cannot afford to shrink. Therefore, alternative distractions for the consumer have had to be found.

Beginning in the late 1980s, one of the most successful of these has been the notion of the designer as celebrity. As a convenient measure of fame, it is noteworthy that fashion's major players, like the supermodels, are now internationally known by their first names, Tommy, Calvin, Donna or Giorgio.

Their clothes tend to be rather dull and dependent on recycling old ideas, so the public is instead encouraged to admire their myriad homes, their yachts, their parties, their "glamorous" lifestyles.

The supermodels were created as part of the same process, as a means of providing an alternative focus within the fashion industry. Although they had been gradually building up their collective profile, the moment when a specific group of models first captured public attention was January 1990 when five of them - Christy Turlington, Cindy Crawford, Naomi Campbell, Tatjana Patitz and Linda Evangelista - appeared together on the cover of British Vogue.

It was as though readers were being told: "Never mind the clothes, look at the fabulous beings wearing them". Around the same time, George Michael released a video parodying the fashion industry, and many of the same models appeared in this.

THE supermodel tag was enhanced by the company these women began to keep. Naomi Campbell began her decadelong trawl through some of the world's most famous men, beginning with Robert de Niro and Mike Tyson (she may now regret being seen with the latter) before becoming engaged for a few months to U2's Adam Clayton.

Helena Christensen went out with Michael Hutchence before he was snatched away by Paula Yates. Christy Turlington went out with various actors before she had the sense to realise this was no way for a girl to have a private life.

Soon enough, models were as well known as the men they dated and the designers for whom they worked. And their fees rose proportionately. Fashion houses began demanding exclusivity and paying the money this demanded.

By the mid-1990s, any supermodel worthy of the name was worth millions. When Forbes magazine conducted a survey of the top models' earnings, their list was topped by Cindy Crawford who made an estimated £4.5 million annually.

Naturally, this information did not meet with universal approbation. In the course of a 1991 press interview, Linda Evangelista had casually remarked: "We have this expression, Christy and I: we don't wake up for less than $10,000 a day."

This ill-judged remark and the venal attitude it indicated were hardly likely to attract admiration for Evangelista et al, but there were other reasons why the age of the supermodel was destined to be brief.

Very quickly, the very designers who had encouraged models to become as petulant and demanding as any other celebrity started to resent their behaviour. There were instances of famous models being banned from shows and their places on the ramp taken by just as competent but less notorious women.

Designers came to realise that the supermodel was a dangerous distraction: what, after all, is the purpose of paying someone a lot of money to model your clothes if she - rather than you - then gets all the attention.

In addition, the reputation of modelling began to grow rather grubby, even before undercover journalist Donal McIntyre's recent expose on British television. The evidence of widespread drug-taking, sexual abuse and humiliation shown by McIntyre had already been discussed in Michael Gross's 1995 book Model. He produced plenty of examples of sordid behaviour in a world supposed to be the apogee of stylish glamour.

But the biggest setback the supermodels faced was that their public, in a traditionally fickle manner, just grew bored with them. Models were no longer fashionable because by the late 1990s their place had been usurped by a whole crop of good-looking young actresses. Curiously enough, they, too, are known by just their first names - Gwyneth, Winona, Cameron - names easy to remember because they are so unusual.

Fashion editors came to realise that more copies of their magazines were sold when one of these celebrities were put on the cover than when a model was featured. The latter, therefore, has been obliged to return to the status she formerly knew.

Even if Amber or Karen or even Giselle wanted to be internationally famous, it is now unlikely she would achieve this ambition. No wonder so many models subsequently yearn to be actresses (and how few of them ever succeed in becoming one).

The supermodel is now, quite definitely, passe.

There is, by the way, one other reason why Naomi Campbell may have thought it timely to announce her intention to cut back on catwalk appearances. She is now 29 and, in the harsh world of modelling, that is way past the customary use-by date.