To survive the throes of winter, there are a few things you need in your sartorial arsenal: a cashmere knit, a reliable coat (be it a trench or a duvet style) and, of course, a trusty pair of boots.

The art deco building I am standing in, in ­Camden, North London, is the inner sanctum of one of the UK’s most successful fashion retailers. There is no shop front here. In fact, the company has no ...