If Swedish retail giant H&M has soared high in the past few years, it's not solely on the back of the massive global expansion that has made it the second-largest fashion retailer on the planet (behind Zara's parent company, Inditex). It is also because it has secured the most unexpected and talked-about high-low designer collaborations - and effectively changed the industry. When Karl Lagerfeld first signed on in 2004 for a guest designer collection, the haute couture world was stunned. And now H&M has announced its latest coup: avant-garde Belgian label Maison Martin Margiela will design a collection for the mass retailer, to be launched on November 15. Vogue fashionista Anna Della Russo's line of over-the-top accessories will be out in October. It's safe to say H&M stores will be busy this winter. Martin Margiela is considered an honorary seventh member of the Antwerp Six group, who went on to affect high fashion radically. The eponymous label was started by the famously secretive designer and, over the past two decades, has become one of fashion's most powerful and cerebral brands. Maison Martin Margiela is known for fusing androgyny and anonymity. After Renzo Rosso, Diesel's founder, took over the company in 2002, he left the brand bearing his name, and the lauded collections are now designed by a collective of designers. The collaboration with H&M comes hot on the heels of moves by several other prominent high fashion designer labels and figures. But as with Rei Kawakubo of Comme Des Gar?ons, who was a major influence on Margiela's deconstructivist style, this pairing is particularly surprising. I find it hard to reconcile the H&M staples of fast fashion trend-based separates and throwaway basics with the conceptual powerhouse and almost anti-trend label that is Margiela. How will Margiela's complex tailoring be simplified and translated to a purse-friendly line for H&M? The Swedish retailer knows how to keep customers on their toes. Not only veterans such as Lagerfeld, Sonia Rykiel and Roberto Cavalli but also respected talents Alber Elbaz, Stella McCartney, Matthew Williamson, Consuela Castiglioni of Marni and even Tamara Mellon for Jimmy Choo have enjoyed success as H&M guest designers. Even pop divas Kylie Minogue and Madonna tried their hands. And although a few elitists might bemoan the blurring of lines between high and fast fashion, most will be pleased with the democratisation of a decidedly undemocratic industry.