It's only possible to gauge the influence someone has had on fashion in terms of longevity when the winds of change blow in the opposite direction. Which is what is happening now.
Looking back on the noughties, one person who has affected not only what we wear but also how we wear it is the former Vogue Paris editor, Carine Roitfeld.
Roitfeld, who resembles a glamorous 21st-century version of The Graduate's Mrs Robinson, was a successful stylist who helped create Tom Ford's Gucci campaigns long before she landed the top job at Paris Vogue (don't call it French Vogue), a publication dedicated to all things luxury. As well as making the French capital once again the capital of cool, several of her legacies have remained intact since her departure in January.
"Glunge", a spin on casualwear bristling with a punky, urban edge but with a nod to full-on luxury, which very much mirrors her own image, remains relevant as a trend.
It's no coincidence Roitfeld's reign coincided with the phenomena of Balmain's Dh5,918 jeans and, in the early days, the It-bag. She is also credited with creating "ironic cool" within luxury labels, as, for example, in $4,000 Chanel jackets that appeared to have been got at by moths; all still going strong.
But her vice-like grip is wavering. Some would argue the current French vibe - younger, geekier, with a nod to Eurotrash French TV and pop culture and its obsession with all things bourgeois, from Chanel quilted bags to perfectly tailored jackets - is even more French than Roitfeld (who is half Russian).
Muses who personify the movement are being hailed as "Le Freak chic" because of their innate Frenchiness - think of the perennially cool Clemence Poésy, Lou Doillon, Vanessa Paradis and anyone young, boyish and beautiful.
Luckily you don't have to actually be French: just dress like you are. This means adopting mannish trousers and wearing them with a tight, white shirt with sleeves rolled up or a neat top, or better still Le Tux. Equally, try giving a nod towards 1950s Teddy Boys, late 1970s punk rock and Disney cartoons on T-shirts.
The poster girl of the movement is Emmanuelle Alt, Roitfeld's successor at Paris Vogue, who has an unfair advantage over us all, having for years styled the shows of Christophe Decarnin of Balmain and Isabel Marant - the very designers who exude Gallic chic, and on whom trendy chains such as Topshop and Zara are keeping a beady eye.
It helps that Alt is geeky. Nerds are very cool right now. And you won't find a chicer nerd than a French one. In France, the colour red and 1970s clown stripes rarely go out of fashion. Magazines are very much telling us how to pull off this season's hottest pieces, such as the dropped-crotch zipped parachute silk trousers (works best with a tight little blazer), or which colours to clash (black, red, turquoise and pink - ooh la la, so French!) or which heel to go for (conical), all from a bespectacled nerd perspective.
I'm not yet entirely convinced but fear I soon will be. Let me explain. Sitting opposite Alt, the 42-year-old newbie editrix during London Fashion Week, dressed head to foot in black (she, not I) and wearing a trilby and neat ankle boots, I kept on getting sartorial flashbacks.
As a young teenager I took part in a French "exchange". Around 1980, I think. How well I remember being shocked at how French girls dressed in the affluent suburb of Avignon I found myself in, compared with urban London, where I lived.
In France there was a culture of trousers (a backlog from YSL?). No cool girls wore skirts or dresses. Even then, skinny trousers were de rigueur, along with what I suppose you'd now call boyfriend shirts and Euro-trashy versions of T-shirts.
French girls aspired to wearing trilbies, tight blazers and ties (which reminded me of my school uniform).
At first I hated the French garb as much as the catchy French pop songs playing on the radio (Plastic Bertrand's Ça Plane Pour Moi?). After two weeks I was hooked.
I returned from France wearing my hair loose, if a bit greasy, falling over friendship necklaces: very Isabel Marant spring/summer 2011, in fact.
Roitfeld's look isn't quite over but Alt, as her name suggests, has come up with an alternative. As they might say in France, Vive la différence.