“For me, life is music,” she exclaims, as she reels off her current obsessions: an eclectic mix, including Nigerian artists Burna Boy and Fela, British singer James Blake, and Kazu Makino, a Japanese musician who formerly fronted alt-rock band Blonde Redhead. In many ways, music was Marant’s first love, and the thing that fortuitously led her to fashion. Picture Paris in the early ’80s: a refined take on sartorial excess cohabits incompatibly with the burgeoning punk movement. A 16-year-old Marant and her then-boyfriend and future fellow designer Christophe Lemaire immerse themselves in the decade’s diverse club scene. “One night it was rockabilly, the day after it was punk or new wave, and another day it was ragamuffin – there were no barriers between all the groups, and we loved playing with all the different looks from the musical trends.” Soon, the pair felt inspired to make clothes together, for themselves and their friends.

“We started to do it for fun, more to create our [own] looks,” she recalls. “Eventually, we were selling a lot of it and we said, ‘Oh, you can make money out of having fun – wow, cool.’ Then we started to discover fashion.” An anti-fashion movement, led by designers such as Vivienne Westwood, Yohji Yamamoto and Comme des Garçons, was bubbling up and it appealed to her rebellious nature. Growing up in the affluent Parisian suburb of Neuilly-sur-Seine, Marant shocked her friends and neighbors by insisting on reinventing her parents’ cast-offs, including wearing her father’s old robes as dresses and her slippers to school. “Sometimes they were not open-minded enough for my looks,” she smiles. It would no doubt amuse the precocious young Marant that, nowadays, chic Parisians can’t get enough of both her main line and diffusion label, Isabel Marant Étoile.

She works from 8am to midnight, five days a week. To switch off and stay healthy, she has imposed a strict no-working-at-weekends rule. Instead, she and her husband, handbag designer Jérôme Dreyfuss, and their 17-year-old son Tal head to their rustic countryside cabin in Fontainebleau, 40 miles southeast of central Paris, where they live simply with no electricity or running water. “I do a lot of gardening. I must say, it’s helping my head – it’s very joyful to see a real result of what you have been doing. I walk a lot in the forest. I swim in summertime.” And they welcome friends, for whom Marant cooks. “I am very good at cooking in five minutes for 20 people. I don’t like to spend hours at it; I am very efficient.”

This espousal of insouciance and skilfulness underpins everything chez Marant. While her clothes may look relaxed, their construction is impeccable; quality is paramount to her. “I prefer to buy a really good thing than a lot of small shitty things that you are going to be fed up with in a minute. I was always like that, even when I was young and I started to be interested in fashion,” she says, recalling items she saved up for in her youth and still wears to this day. For Marant fans, building a forever wardrobe is easy. Her unmistakable silhouette – sharp shoulders, nipped-in waist, slouchy pants – and ’80s boho-glam-rock aesthetic has never wavered, becoming more and more recognizable, and more and more refined with every collection. “You can really mix [my designs] from one season to another, because it’s the same eyes and the same soul [that create them]. I do things in a very sincere way.”

In case you were wondering, the FW20 collection she presented a week later is utterly divine. Taking an unexpected turn towards minimalism – inspired by William Forsythe’s ballet, Blake Works I, and a desire for “real” clothes – the neutral palette and elegantly cut capes, cuddly coats and luxe knit dresses have a timeless appeal. Backstage, she told journalists that she wanted to make cozy but sophisticated clothes that women won’t ever want to throw away.

Marant truly cares about how her clothes make women feel. How they fit and flatter feminine contours. Before her portrait with French American model Sophie Koella is taken, she instinctively swoops in to cinch the waist of Koella’s oversized printed utility jacket (from the SS20 collection), sharpening the silhouette but also allowing it to slouch ‘just so’. “Even though I’m someone who dresses on the unisex side, I’ve always felt very comfortable in Isabel,” says Koella. “Her clothes make me feel feminine in a way that feels natural to me and my personality. I’d always choose a baggy jean over a skirt, for example. But, for some reason, I can wear an Isabel Marant skirt and still feel like myself.” For every micro-mini and knee-high boot, there is an oversized knit or loosely tailored pant to temper the more risqué undertones. And they aren’t supermodel-only clothes, either – Marant refutes outmoded age limits (she turns 53 next month). “What excites me is to see how wide the panel of people wearing my clothes is – in terms of age, most of all, because it’s from 15 years old to 80.”

And she truly cares about women. For the second year in a row, she has designed an International Women’s Day T-shirt in collaboration with NET-A-PORTER, the profits of which go directly to charity Women for Women International. She speaks passionately on the topics that matter to women nowadays, too, from the gender pay gap – “in my company that was never a question. I never look at the sex of somebody, I never look at the color. I was raised like that so for me it’s natural” – to the Me Too movement and female objectification. She praises the strong French female role models who inspire her endlessly: feminist writer Simone de Beauvoir, politician and women’s rights defender Simone Veil and provocative artist and sculptor Louise Bourgeois. “I love women, any kind of women. When I’m asked, ‘Who is your muse?’ Women are my muse.” And women love Isabel right back.