There's a major revival going on this spring. Even fashion detectives claim they didn't see it coming.
It's not the seventies, or trousers, or even the maxi. Neither is it androgyny - although this has contributed - or nineties minimalism or eye-popping brights.
Although all of these trends are important from a high-fashion perspective, they have failed to connect with the average customer; ie, the woman who loves to dress up but doesn't want to feel like she is going to a fancy dress party - or Lady Gaga pageant.
What women are connecting with is the shirt - particularly mannish styles that straddle the gap between day and evening, smart and casual, quirky and couture.
We are in the midst of a huge shirt revival unseen since the 1980s. Shirts have already knocked T-shirts off the radar and, with cotton prices at a record high (cotton rose by a staggering 30 per cent last month alone) could soon be joining "it" bags and designer heels in the luxury tier.
For once catwalks can't claim to be behind the latest phenomenon. Although there were plenty of shirt shapes in the ready-to-wear spring/summer 2011 collections - Prada's striped, boxy styles being the boldest and Victor & Rolf's the brightest - these aren't the styles flying out of shops and into most women's wardrobes.
Shirts were a talking point at Balenciaga, where Nicolas Ghesquière featured wet-look polythene versions with cowboy-style rim-tipped collar points, and at Givenchy too, where Riccardo Tisci created a tricksy waistcoat/jacket hybrid.
Shortly after the birth of her fourth child, Stella McCartney came up with a maternity-look denim tunic/shirt that I can't see going beyond the catwalk, and Phoebe Philo took shirts to a strange new territory at Celine.
One designer who has influenced shirt trends in the real world is Guillaume Henry. About a year ago, Henry became head of design at a long-forgotten Parisian house called Carven, fleetingly famous for a perfume called Ma Griffe, which I can remember my grandmother wearing.
By using the shirt as a sort of muse, dissecting it into pieces (did you know the traditional Jermyn Street collar alone has 14 pieces?) and using demi-couture fabrics, Henry helped put himself and Carven on the map.
His signature, prim little white collars and witty cuffs, in shirtspeak known as the "Winchester" style, has had a huge impact on the high street (Alexa Chung wears little else besides Carven these days).
Similarly, companies who spied the potential of shirts for women are doing well.
MiH Jeans, which sells at upmarket shops such as Boutique 1 and Harvey Nichols, saw shirts as a way to differentiates itself from premium denim rivals two years ago. Now its shirts sell out long before its coveted denim, the founder Chloe Lonsdale, tells me.
"We've been through lots of trends over the last few years from super casual dress-down LA-style, where you even wear jeans to the workplace, to only wearing dresses."
"A lot of catwalk trends are off-limits to most women. For instance, the shift towards trousers was kick-started by the very elegant high-waisted Celine styles, which were all teamed with shirts. But this look wasn't attainable to everyday women."
Lonsdale decided to offer a version that was: smart jeans with an equally smart shirt. This sort of nouveau casual is the latest way to dress. As Lonsdale points out, it doesn't work with any old standard shirt. "It's more about teaming the right texture, like muslin, with special pearl buttons," Lonsdale told me. "Little details to make it feel and look special."
No one knows this better than Thomas Pink, the LVMH-owned luxury shirt brand that boasts the largest shirt shop in the world (on New York's Madison Avenue) and whose womenswear range has long been a corporate-chic staple.
Equipment, the French 1980s shirt brand owned by Carine Roitfeld's husband, is also enjoying a "moment".
"You should never try to reinvent a shirt - just make it seasonally relevant," explains Lonsdale, who has incorporated on-trend mini-capes and a leather thong lace-up collar into her autumn/winter range. "Or remove it from the idea of what a shirt is. One of our best-sellers is a style inspired by YSL's classic patch-pocket safari shirt. This was part of our first ever range."
The legendary designer Yves Saint Laurent once said he wished he had invented jeans. Perhaps his legacy, the men's safari shirt which he reworked for women, will ultimately be their nearest rival.