Olive brown, £340, Milano cream, £350, both Jil Sander+ x Birkenstock 1774

The resulting four styles are all hyper appealing. The couple’s personal favourite is the Berlin, a clog interpretation of an original Birkenstock design. For my money, however, it’s the white ones that qualify as an immediate classic. Partly it’s the perversity of that expensive-looking white leather, which is the antithesis of the porridge-coloured functionality of the originals. Like virgin snow, they make you want to jump straight into them.

Fashion has been hijacking humble items for the best part of a century, from the Breton sail’s T-shirt to denim. But the Birkenstock additional political undertones bring an extra edge. It’s a shoe that has always been associated with nature, which is huge in fashion right now, with beaches and forests being co-opted as backgrounds for advertising campaigns in lieu of the sexy sky scrapers of old.

It also puts comfort and “foot-health”, considerations traditional designer footwear has shied away from, centre front – and that works with fashion’s current preoccupations. As Luke says, “It’s not the moment for towering stiletto heels.”

“Why would you do that [wear painful shoes] to yourself,” adds Lucie. “Are you dressing for yourself or for someone else? I don’t know that many women who would dress like that for themselves”.

Lisa Armstrong’s column appears each Saturday in The Saturday Telegraph and is published online every Saturday at 6am on Telegraph Fashion.

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