Mark Ritson on branding: Clothes horse? Yes Couturier? No

Last week, on Monday evening, a willowy figure clad in a red chiffon dress stood nervously beside a somewhat less svelte man in a black suit and open-necked shirt.

The two watched as the first 150 excited shoppers rushed down the escalators toward the basement of Topshop's flagship Oxford Street store. Outside, thousands more waited their turn.

'Are you pleased?' Kate Moss asked Sir Philip Green as the throng reached the sales floor for their allotted 20 minutes of shopping. Green gave the model a big bear hug. 'Thank God,' said Moss.

The celebrity designer tactic is as close as you can get to a foolproof branding strategy right now. Like previous celebrity designers and their high-street patrons, the Kate Moss collection for Topshop is going to please everybody.

Shoppers get to buy into the star's look. The celebrity designer gets a refreshing blast of street cred, sees their designs worn by the masses - a thrill for even the most exclusive and jaded designer - and earns a small fortune. In Kate's case, she gets 拢3m, more publicity and widespread acknowledgement that she is more than just a pretty face.

The retailer usually gets a huge injection of international editorial coverage, a chance to reconnect with top-tier consumers and enormous sales at significant price premiums in a short period of time. Celebrity designers also confer a much-needed sheen of exclusivity to an otherwise mundane and mainstream offer. For all their fashion-forward clothing, the Topshops and H&Ms of this world are anything but exclusive. Kate Moss' collection, in contrast, is limited in almost every possible way: 150 people at a time, limited to 20 minutes' browsing and a maximum purchase of five garments each. This is a golden opportunity for Topshop to be not only fashionably cool but also cool in a very limited fashion. The real reason for Philip Green's hug was neither the sales nor the suddenly very exclusive glow emanating from his shop. It was the international editorial the Moss collection garnered. 'We want to build this into a global brand,' he told Women's Wear Daily when he announced the Kate Moss deal late last year. And global brand awareness he now has.

Despite the success, however, Kate Moss marks the apogee of the celebrity designer movement. A subtle shift has taken place over the past six months. The initial celebrity designers, including Karl Lagerfeld and Stella McCartney, who created collections for H&M, were celebrities because they were designers. Moss joins the growing ranks of stars, including Madonna, Kylie Minogue and Lily Allen, who are celebrities trying to be designers.

Kylie is a world-class singer, actress and minx, but certainly not a world-class designer. There is a big difference between being a consumer and a producer. I love Champagne, but have no clue how to blend grapes. With a designer who is a celebrity you get cutting-edge designs and savoir-faire. With a celebrity trying to be a designer you merely get a rehash of items from their wardrobe.

If you looked carefully enough at the reaction last week to Kate Moss' collection in the press, the cracks were already starting to appear. New York Post named the collection 'Duplikate' and accused of Moss of 'copying a lot of other people's stuff Kate's worn before'. New York magazine was even more scathing with its one-word review: 'Snore.'

As Moss and Green watched the Oxford Street throng last week they witnessed the birth of Topshop's international profile and the beginning of the end of the celebrity designer.

30 SECONDS ON ... DESIGNERS ON THE HIGH STREET

- Karl Lagerfeld, who has worked with fashion labels including Chloe, Fendi and Chanel, collaborated with H&M in 2004 to offer a range of clothes in chosen outlets for men and women. Almost all the pieces sold out within two days.

- Stella McCartney also created a collection for H&M. The one-off autumn line, which debuted in November 2005, was a combination of sharp tailoring, irreverence and cool femininity.

- Debenhams carries more than 26 designer brands, including J by Jasper Conran, Pearce Fionda by Ren Pearce and Andrew Fionda and BDL by Ben de Lisi.

- Japanese designer Yohji Yamamoto collaborated with Adidas to create the exclusive Y-3 range. The 'Y' stands for Yamamoto and the '3' represents Adidas' trademark stripes. The collection includes clothing, footwear and accessories.