The next chapter of ‘underwear as outerwear’ can be worn by almost everyone

When things get hot in the fashion capital Paris, you don’t need a meteorologist to predict a seismic shift in style ahead.

Actor and muse Audrey Hepburn had customers pining over pale-blue lacy nightgowns when she starred in the 1964 film Paris When It Sizzles . More than 60 years later, the city has worked its magic once again after a summer heatwave had the front row at the haute couture collections abandoning overly layered looks and bringing nightwear into the harsh light of day.

“I noticed that all the cool girls were wearing what looked like sleepwear in the streets,” says Sunday Life fashion editor Penny McCarthy, who braved rising temperatures on the Left Bank in her eternal quest for the next big trend.

“This is different from the ’90s slip dress revival. I was seeing nighties, lace slip skirts, camisoles and silk knickers [referred to as ‘boudoir shorts’ in polite society] styled with everyday clothes and I thought, T res chic. ”

With a warm spring looming – no need to wait for a heatwave – McCarthy and Hepburn are the style guides you need. By combining items normally hidden beneath sheets of the highest thread count with unexpected essentials, you too can look like a hot Parisian.

Step one: Look for nightwear-inspired pieces, or elevated bedtime attire (no Disney princess prints or oversized T-shirts), in natural fibres such as silk, cotton and the lightest of linens. Receive bonus points for lace trims that could have been made in a convent rather than for a late night movie on SBS. This is the anchor of your outfit. You should look as though you could have rolled out of bed wearing your nightie, or silk skirt, except for the fact it is smooth and pristine. Cleanliness is important here.

Step two: Keep the palette calm and restrained, steering clear of neons and bold primary colours like traffic-light red – it’s all about soothing the eye rather than getting observers overexcited. Cool blues are as refreshing as spring water, ivory adds to the impression of purity, and pale pinks enhance the feminine appeal.

Step three: When it’s hot, your skin takes its cues from Hollywood icon Greta Garbo and just wants to be left alone, so the silhouette should be loose (bike shorts are not a consideration). Skirts and camisoles should skim the skin rather than grip it and even the shortest of shorts should be voluminous enough to catch a stray breeze.

Step four: Like any self-assured Parisian woman, you don’t want to be mistaken for a damsel in distress. This is the fun part, where you add an unexpected hint of masculine energy. Rugby tops, blue jeans, structured coats and tailored shirts add a certain je ne sais quoi and provide extra warmth and coverage when the weather’s as cool as you look. Leather sandals or sneakers will also make it clear you’re not sleepwalking, merely dressing like a dream.

Fashion editor: Penny McCarthy. Hair and make-up: Aimie Fiebig using Sisley Paris. Fashion assistant: Abbie Stockwell. Model: Angelina at Priscillas.