Kate: The brutal truth about her fading looks

Last Sunday night, I had a revelation that was both shocking and, let's face it, inevitable. There I was, listening to a concert at the Royal Festival Hall, and a few rows in front of me was someone I could have sworn was Kate Moss. But I kept craning my neck to look at her, thinking: no, it can't be.

The giveaway in the end was that she was sitting next to her lover Pete Doherty and was whispering in his ear. Yet, other than that, the tired-looking woman with brassy, over-dyed hair who was wearing a cheap, nasty vest (one of her own designs, perhaps?) bore no resemblance to the Kate Moss in the latest Topshop advertising campaign, or the latest Belstaff campaign, or the latest Dior campaign, or on the giant billboard outside the Burberry store in Knightsbridge.

That impression was strengthened by remarkable new pictures yesterday of Kate on her way to Paul McCartney's 65th birthday party, revealing almost skeletally thin upper legs, and knobbly, wrinkled knees which would put Nora Batty to shame.

What a contrast to Kate Moss the fashion icon, who is pretty damned perfect, the woman all young girls want to look like. Her skin is flawless, her eyes clear, her thighs smooth.

And, yes, when Kate first started modelling aged 14, she was, in the flesh (OK, not much in the flesh given how scrawny she was), exactly as she appeared in the photographs.

That is the joy of being 14 or 15 or 16, and the reason girls this age are the most in demand when it comes to fashion shoots, or magazine covers, or catwalk shows.

When I edited a fashion magazine, I soon learned that any full-page picture on the beauty pages, which would expose every pore in a model's face, had to be shot using a very young girl. Or, and this is a big or, you would be involved in many studio hours of retouching, which is very expensive.

So why do magazines and big luxury brands continue to use a model who is past her sell-by date?

The harsh reality is that only really famous models (of which Kate is the leader of a pack of about three) and celebrities are able to shift magazines or skin cream. It is why they warrant the extra expense and time of retouching.

Rather than dropping Kate as she became an increasing liability close-up, the magazines and the big brands have shored her up, airbrushing her within an inch of her life so they can sell their product.

The result is that we have all been party to the lie that Kate, despite being a mum, and despite her hard-drinking, alleged drug-taking, late-night partying lifestyle, has somehow, miraculously, because of good genes or good bone structure or sheer bloody luck, escaped completely unscathed.

The wizardry of technology has, unfortunately, spawned a whole generation of models who know that little sleep and too much champagne gives them cellulite, and crepey skin, and spots, and dark circles, but who regard computer airbrushing and clever make-up artists as their safety net.

Models might pose for a photo eating a watermelon while drinking two litres of still mineral water, but I know very few who live this way in real life. They can't be bothered. They have money, they are beautiful, they are spoilt, and so they like to fill their time quaffing cocktails on yachts, not detoxing in spas.

Kate is, of course, the queen of this pack. She has been blessed with a naturally photogenic face. She has a gorgeous uptilted nose, lively eyes, high cheekbones and a rosebud mouth. But she is not perfect.

We fashion editors loved her in her 20s for the fact she would brazenly model a bikini on the catwalk or in bright sunshine, despite the fact she was no longer 16, had never been six foot, had a long trunk and short legs and the dimplings of cellulite.

But I think it is time we revealed her for what she is. As a woman in her mid-30s who has not looked after herself. Now, normally, I would say good luck to her and leave the poor girl alone.

What is wrong with growing old gracefully? It is all any of us imperfect specimens can aspire to.

The reason I have a problem with Kate is that for millions of teenage girls in this country, the images they see of her in a bikini 20ft high in the window of Topshop are taken as the living, shining, dewy proof that you can take drugs and drink and smoke and never eat any carbohydrates, and it won't make you any less beautiful.

Young girls don't care about what their bone density will be when they are in their 60s, they don't care about developing lung cancer in their 50s. They care only about how they look at 18 or 22.

How much more wonderful, and brave, would it be were Kate to say, sod the great lighting and the expensive airbrushing, this is what I really look like: if she were to say "My eyes have bags, my skin has fine lines and breakouts, my teeth are yellow and my health, well, who knows what my lifestyle has done to my inner beauty".

My guess is that sooner than any of us, and especially her, could imagine, Kate will soon resemble those old girls from the Sixties - the Anita Pallenbergs and the Marianne Faithfulls - and will start to disintegrate before our very eyes.

By then, though, it will be far too late for all those wide-eyed young girls who queued only last month at Topshop to pay good money for her clothes so they can buy into her supermodel chic.

The trouble is that they, with their natural imperfections, will never look like Kate Moss the icon. The irony is that the real Kate Moss doesn't look like her any more, either.