Marks & Spencer has discovered a secret: women will buy as many velvet shirts as they can produce. Hardly surprisingly, it's not a secret anymore. Holly Davies unravels the tale behind the shirt on everyone's back.

Two winters ago, Gucci mania was at its height. The must-have buys for any self-respecting fashion mavin were a pair of hipster trousers and a luscious velvet shirt. The price for the shirt alone was around pounds 500. The way to wear it was nonchalantly unbuttoned, as low as you dared.

Last winter, Marks & Spencer cottoned on and offered an equally chic - but more forgiving - version. It cost a mere pounds 40 and was an instant success. Women started buying them by the handful. For the price of one Gucci shirt, you could afford an M&S equivalent in every colour for you and a friend. By Christmas, mothers and daughters were wearing matching shirts. And so were their friends. If you didn't own one yourself, you knew someone who did.

They were originally available in just four different colours. My mum bought one in chocolate, my sister in law bought one in blue, and my aunt bought one in black. I chose to be different and resisted the temptation. Last Christmas was like being squashed in a jewellery box between four velvet walls. Everyone turned up for Christmas dinner in the same shirt.

Again this year they have appeared on the rails of your local branch of M&S. This season, there is a version in devore velvet too. The problem is they are totally irresistible. Every week at London's Marble Arch branch alone, 1,000 of them are bought by women thankful that they have bought a piece of clothing they know they will wear forever and a day. The shirt is equally useful for daytime or night, worn with trousers or skirts. They cover all the lumps and bumps, they feel comfortable, look glamorous and they wash well.

This shirt cannot lose and has been imitated up and down the high street. Other versions include one by Jeffrey Rogers, which at pounds 24.99 is cheaper, and by Karen Millen, made of stretch velvet and in a slimmer cut (pounds 89.95). English Eccentrics have always made a luxury velvet shirt, and theirs start at pounds 180.

Our model, Annabel Freiberg, is a hopeless addict. She owns five M&S variations and still her appetite is insatiable. "I go into Marks & Spencer every two weeks and the only thing I seem to want to buy at the moment is another velvet shirt. I've got my eye on a new one that is slightly different because it's got a devore velvet cuff and collar, and is a bit more jackety than the others. I just find them so useful. I like to wear lots of chunky jewellery and the colours of the shirts really complement anything I decide to wear. They are also absolutely brilliant because I go to a lot of events that I have to attend straight after work and because they are velvet they look dressy enough for the evening."

Janet, 51, is another fan. She bought a chocolate brown shirt last December and has been wearing it ever since. She works shifts and can work in the afternoon or up to midnight: "It's quite hard to find things to wear. You are stuck between comfy pyjama-style outfits and shoulder-padded suits, neither of which make you feel smart and comfortable. My velvet shirt crosses both borders."

However, you can have too much of a good thing. The velvet shirt might well become a victim of its own success. As a slightly jaded Janet pointed out: "I would quite like a bottle green one but now that everyone has them I don't think I'll bother."

Debbie is the PA to the chairman of a large travel company located just down the road from the Marble Arch branch. She bought a creamy gold-coloured panne velvet shirt a couple of weeks ago, but is starting to regret it. "I wore it to work the day after I bought it and immediately bumped into someone in the same shirt, which was really embarrassing. Since then I think I've worn it once to the pub. I figured it would be so dark in there that no one could tell anyway."