The Swedish brand H&M is masterful in its marketing. For all that Topshop, Uniqlo, Target, Gap and others have got into the designer-meets-high-street game, and Debenhams pretty much started it, it is H&M that has laid down the rules.
More effectively than anyone else, H&M has garnered the credible names - Sonia Rykiel, Karl Lagerfeld, Viktor & Rolf and, now, Lanvin; it has built the riot-inducing hype; and, most of the time, it has produced decent clothes in relatively small quantities that people would fight to get hold of, whether to treasure or to sell on eBay. The only time the brand went for the celebrity option - Madonna - the results were fairly dismal, and since then H&M has been dogged in its pursuit of those designers that will appeal to the truly fashion savvy as much as the masses.
So just what is it that will make people queue up for hours in the rain to get first dibs on the Stella McCartney at H&M collection, leaving the Roland Mouret at Gap collection of 2006 a mere blip on the high-street radar?
Why was everyone thrilled about Matthew Williamson for H&M but relatively indifferent to Matthew Williamson for Debenhams?
Well, partly of course it's the fact that H&M keeps things moving. Sure, the Designers at Debenhams range has been around since 1993, and is a great, reliable source of pretty Julien Macdonald party dresses and Jasper Conran jeans, but it's also safe, classic and, in its very reliability, lacking in momentum. It's old-school: capsule collections by middle-of-the-road designers that sit in the shop until the end of the season, at which point they will be put on sale. Back in the 1990s it was exciting, but in the era of fast-fashion it's just not, well, fast enough.
But when Karl Lagerfeld agreed, back in 2004, to take what he called a very "modern" step and design a collection for the Swedish retailer, previously known for its teen-friendly fashions and low-priced basics, it seemed an almost inconceivable move for many. Why would someone like Lagerfeld, probably the most famous fashion designer in the world, thriving at Chanel and Fendi, decide to make cut-price clothes for a high-street retailer?
Well, because if those clothes are virtually impossible to get hold of without camping outside the doors of the 20 stores worldwide in which they were available, then all it does is add to the popular appeal and mystique of Lagerfeld himself and his brands - helping boost sales of the low-priced, high-profit-margin make-up and fragrance.
And let's face it, what real fashion fanatics want is something that other people can't get hold of. The fact that even six years later there are Karl Lagerfeld for H&M items on eBay being sold for hundreds of dollars is testament to that.
It's not just the designer names - Stella, Karl, Roberto, Sonia - that have worked so well for H&M: it's the celebrities brought on board to promote the products. The launch of McCartney's range, in 2005, saw her celeb friends such as Gwyneth Paltrow turn out for the party, the likes of Paris Hilton appeared at the Jimmy Choo launch, and so far the Lanvin collection has been worn by celebs including Sofia Coppola, Pixie Geldof and Roisin Murphy. The clothes are red-carpet-worthy, too: Roberto Cavalli's 2007 collection, for example, featured a long, gold pleated dress that was limited to just 800 numbered editions and was almost identical to one worn on the red carpet by Kate Hudson. At the time of press, number 494 is on eBay with a starting bid of $699 (Dh2,600).
Of course, the other brand with that kind of star power is Topshop, which started its collaborations gently with an exquisitely boho collection by the 1970s print designer Celia Birtwell, who had been the wife and co-designer of Ossie Clark. It was wildly successful, with items sold out within minutes in the shop, and then again online. Pieces such as the much-coveted Red Rock dress were soon up on eBay for three times the original price. An even bigger hit has been the three-year agreement with Kate Moss, whose first collection for the shop was critically panned, for being derivative, but saw people queuing eight hours before the clothes went on sale at the store in London's Oxford Street.
But the thing that keeps the fashionistas coming back and the bloggers blogging is the adventurous spirit of some of these collaborations. Moss and Lagerfeld aside, these are not household names. Certainly your average Vogue or Grazia reader will know many of them, but Topshop's employment of the likes of Preen, Christopher Kane and Gareth Pugh works for all parties: Topshop basks on its fashion-forward laurels, the designers raise their profiles and receive financial benefits that help them to stay in business, and the shoppers get to own a piece of credible designer fashion that would otherwise be beyond their means.
Target in America also has a nice line in this sort of collaboration - their Isaac Mizrahi range launched before Lagerfeld's H&M one, and they have worked with the likes of Alexander McQueen and Jean Paul Gaultier, as well as smaller, edgier brands such as Luella Bartley and Proenza Schouler.
The big question, though, is what does the shopper actually get from these collections? After all, by definition, the shops' normal fashion lines have been designed by real, live designers, whose resources for creating fast fashion sometimes put them so far ahead of the prêt-à-porter designers, in terms of trends, that the catwalk collections now take as much inspiration from the streets as the shops do from the catwalks.
Indeed, look in H&M right now and there are styles that are not, in fact, a far cry from Lanvin's signature looks and colours. And on past high-street collaborations, production quality has been mixed, with some designers maintaining fabric quality and cut and others finding it impossible to replicate ready-to-wear styles at high-street prices.
But if there's one thing that will sell clothes, it's that sense of excitement and hype of which H&M is an expert creator. The hype is reminiscent of the era of the It-bag, but the products are accessible to almost everyone. The gradual release of news - the first hints that Alber Elbaz might be considering a collection, the confirmation, the leaked lookbook and campaign images, the requisite short film - all eagerly pounced upon by bloggers and Tweeters: you can't buy publicity like that.
All of which is a roundabout way of reminding you, in case you'd been living in the desert for the past couple of months, that Tuesday is the date that Lanvin's collection for H&M arrives in the Abu Dhabi Mall, Dubai Mall and Mall of the Emirates stores. You've got to see it to believe the hype.