Roger Walker Dack has been running an exclusive fashion club for 10 years. It has 15,000 members of all ages, sexes and fashion persuasions and has never advertised. His events take place in a King's Cross warehouse, last three days and make in excess of pounds 100,000 a time.

Sounds seedy? It isn't. This is a fashion insider's secret, every fashion fan's dream. A huge warehouse full of designer confections from Katharine Hamnett dresses to Comme des Garcons shirts (among dozens of other names) all at up to a quarter of their retail price.

Walker Dack runs the Designer Warehouse Sales, or DWS; he also founded Fashion Acts, an HIV and Aids charity. Walker Dack began selling fashion at knock-down prices in 1987, when, as a former buyer for The Burton Group, combined with chairing the English Menswear Designer Collections (EMDC) he saw a way for young designers to turn their sample collections back into cash. A sample collection can cost up to pounds 20,000 to produce and for any self-funded designer, this is a lot of money. The clothes cease to serve their purpose as soon as the collection is bought by the stores, and selling them is a quick way of making returns. Before you spend your entire winter clothing budget, put some money aside for the sales that begin at the end of the month.

"I never deal with manufacturers or retail outlets," says Dack, who also designs his own menswear collection, "just designers. I also help designers who have been let down by shops, and occasionally take the stock of a designer who has gone out of business." It's a tough world out there for small fashion businesses, and Dack, it seems, is their saviour. "We usually have the sales around the time of Fashion Week, so the money they spend on London Fashion Week can be recouped.

The sales are split into three; one for women, one for men, and a fabric sale. Each attracts its own crowd. The women's sales are the most diverse, attracting fashion fans of all denominations eager to pick up a specific bargain, and women who find shopping in department stores alienating. Be prepared though, the changing room is makeshift and communal. Punters can hunt through rail upon rail of clothes, shoes and accessories for that elusive must-have item, and fight for it if necessary. "We've had loads of dramas around that hold rail," Walker Dack says with a low chuckle.

The clientele is not restricted to those on a budget. The mailing list includes Lords, Ladies and Baronesses, who Walker Dack can identify when they attend his sales (he is always around to help when they get crowded, but when the going gets tough he goes for a cup of coffee), but he doesn't recognise the models and footballers about whom his staff try to keep him informed.

The fabric sales are entirely different. Coachloads of fashion students and ladies-who-lunch vie for specialist fabrics exclusive to the sales, which cost from only 50 pence a metre.

The Designer Warehouse Sales, The Worx, 45 Balfe Street, London N1. Womenswear: 26-28 September; Menswear: 3-5 October; Fabric: 16-18 October. Prices start at pounds 50 for a jacket, pounds 30 for a dress, pounds 20 for a shirt, pounds 75 for a man's suit and pounds 25 for a woman's top. For further information call 0171-704 1064.