By Terence Blacker, The London Independent, 2002

I was 18 and about to go to Cambridge. It was time that I became a man. My father took me to London for an important rite of passage - a visit to Huntsman's of Savile Row, where I was measured up for a couple of suits. Material was chosen, first for a coal-grey suit, then something green and hairy, suitable for the country. The tailor, a murmuring, obsequious man, went through his measuring-up routine with the seriousness of someone conducting a religious service. Another visit was required and then, a month or so later, I stood before a mirror, first in the dark suit, then the green one, both with waistcoats. The suits would last 30 or 40 years, the tailor told us. I would simply need to come in to have them let out now and then.

Even as I thanked my father for what was a generous present, I was aware of a puzzling sinking of spirits - 30 or 40 years? No clothes were meant to last that long. I liked things that wore out so that they could be replaced. There was something else. The boy - the man - who looked back at me in that green tweed suit was not really me. I looked like a fraud. Hopelessly ill-equipped as I was for the outside world, having just emerged, blinking and virginal from 11 years at boarding schools, I knew that those suits and I did not belong together. They were too damned solid, too baggily confident. They represented a choice of future and character - a Huntsman life or a non-Huntsman life.

It was an easy decision for many of my contemporaries. Slipping into middle-aged clothes with the ease of someone growing into an adult skin, they clumped around Cambridge in heavy brogues, hands sunk deep into the pockets of their cavalry twills as confidently as their fathers had once done.

Now one of them is to promote this style of clothing under his own brand. Duchy Originals, the company set up by Prince Charles to promote and sell organic biscuits, soft drinks, cheese and sausages, is planning to move into what it calls "high-quality non-food products". A royal "country casual" range of tweed suits, scarves and jerseys is soon to be available. Cashing in on the new obsession with gardening, the firm will also be selling up-market garden furniture.

The idea behind this initiative is sensible and philanthropic. Promoting wool products, Prince Charles will be helping struggling hill farmers, while wood sold for furniture, mostly oak, will fetch significantly more than would normally be paid by avaricious timber merchants.

It is the country casual look that is worrying. There is something about the heavy, well-made clothes favoured by the upper middle classes which seems to seep through the skin and into the soul. Wear a tweed suit or brogues for any length of time and soon the timbre of your voice begins to change, becoming flatter, louder and more bored. The light goes out of the eyes. Soon you lose the ability to listen to anyone unless they are expressing views with which you agree on a subject with which you are familiar. There are grim sexual effects, too. First you are clumsy, all elbows and knees, then briskly functional, before losing interest altogether, preferring to invest your emotional life in animals. You marry a wife who can only read the Daily Mail and the novels of Jilly Cooper, which she finds "absolutely killing".

Your laugh becomes loud and humourless. You develop a rather strange obsession for playing unkind practical jokes. As the country casual effect takes over, you may be faintly aware that your friends, your family, your ideas, your taste, your life are becoming duller by the minute, but oddly the fact worries you less and less. There is something comforting about dullness; arty-farty members of the chattering classes may scoff, but dullness is where you live, where you feel most comfortable.

Soon you'll be sending your children - or "brats" as you call them - to boarding-school because you think it will help them to stand on their own two feet. One day, they will reach an age when, you decide, they should be taken off to Savile Row to be measured up for a Duchy Original country casual suit, and so the whole ghastly process will repeat itself into another generation.

There are rumours that the luckless Prince William is about to become a victim. Until recently, his dress sense has suggested that he favours the Prince Andrew look - a sartorial halfway house where blazers and polo- neck sweaters are worn without embarrassment - but now, heartbreakingly, he is said to be "experimenting with tweed".

This is a phase that many young people of a certain background have been through - like experimenting with drugs or homosexuality, but with more serious long-term effects. Those who, in the face of all the evidence, believe that the monarchy has something to offer in the future will be praying that William kicks the country casual habit before it is too late.