What I wore this week: the perfect skirt length

In fashion, as in food, best-before dates as proclaimed by the manufacturer should be neither slavishly followed nor wilfully ignored, but instead viewed through the prism of your own considered judgment. As a rule, the flashy stuff goes off more quickly. You don’t want to risk 10-day-old prawns; by the same token, the headline-grabbing must-have pieces fall hard when they fall. (I’m thinking of those Isabel Marant wedge-heeled hi-top trainers that spawned a million copies and that everyone wore, me included: they’re now unacceptable in polite society.)

But most cases are less black and white. If the yoghurt in the fridge is a few days past the date on the top but smells fine, I’d eat it, but I wouldn’t give it to kids or guests. The same goes for fashion trends. If practicality or speed demands, I can survive a day in a outfit that is curling around the edges without my self-esteem crumbling. But some people are sensitive to the merest whiff of style that’s anything less than box-fresh, and I would not wish to offend such delicate sensibilities, so I take my diary into account.

Consider the case of knee-high boots when worn with an above-the-knee skirt. For a long while, this was one of those outfits that was ubiquitous. It just worked: it was flattering, and looked smart and current. But having slid into fashion under the radar, it slid quietly out again. A bit like those jars of spices you don’t think of as having a best-before date, until you notice that the Szechuan peppercorns expired in 2008 and your life flashes before you. My point is, you have been doing the boots-tights-above-the-knee-skirt look longer than you think. No one will shriek with horror, but some may wrinkle their noses.

It’s knees that are the problem. Not yours, specifically – I mean all knees. Your skirt needs to be long enough to meet the top of your boots. It’s a counter-intuitive update, because it feels more old-fashioned, but it works. Fashion needs fresh ingredients, too.

Jess wears sleeveless jumper, £100, by Michael Michael Kors, from harveynichols.com. Vintage suede skirt, stylist’s own. Boots, £135, office.co.uk.

Stylist: Melanie Wilkinson. Hair and makeup: Laurence Close at Carol Hayes Management.