From Matthieu Blazy at CHANEL to Demna at GUCCI, there are a score of designers working in the upper echelons of fashion who share something in common… something from their past… something perhaps you didn’t know about them. You will find them in senior positions at Alexander McQueen, Courrèges, Louis Vuitton and Prada, or with eponymous labels such as Cecile Bahnsen and Mark Fast. But no, this…