Between late October and early May you can’t swing a dead cat in this city without hitting a Capitol Hill bro decked out in The Jacket.

You know the one I’m talking about.

Every industry has its unofficial uniform, as anyone who’s seen bankers in fleece vests swarm midtown Manhattan can attest.

But why Barbour’s signature wax cotton jacket? The Jacket, which retails for $415 at Orvis but is also sold in places such as J. Crew and Nordstrom, has too many pockets to be practical. And unless you buy the separate vest liner ($140), it’s about as useful in cold weather as a tank top. It’s also rainproof but the detachable hood will run you another $50.

It all started in 1894 when a Scotsman named John Barbour began selling oil cloth coats to sailors, fishermen and dock workers in South Shields, England. In 1908, John’s son Malcolm would make J. Barbour & Son’s first mail-order catalog.

But the Beaufort, Barbour’s most iconic jacket, designed by Chairman Dame Margaret Barbour, has only been around since 1983. The Beaufort is “made with medium weight 6 oz. thornproof waxed cotton,” according to Barbour’s website. And “inspired by French shooting jackets,” it has “two generous bellows pockets and two waist-height moleskin hand warmer pockets for everyday practicality.” Oui.

But why is it popular among so many city dwellers? It’s not like staffers are clocking out at 5:30pm and heading straight to a duck blind. Well, it’s not uncommon for working class wear to become elite fashion. I mean, just look at who’s now wearing Carhartt jackets and Timberland boots.

The answer lies across the pond. Despite The Jacket’s French design, Barbour has what’s known as a Royal Warrant, which makes it the official outfitter of the English Royal family. So when no less a global icon than Princess Diana was seen sporting one in the 1980s, the brand took off. Young wealthy, upper-class British women known as “Sloane Rangers” took their fashion cues from the Princess of Wales and another icon was born. The phenomenon is similar but more widespread than the Michelle Obama Effect.

Lady Diana made The Jacket exude a certain elite, aspirational cool that celebrities have continued to provide it. For Instance, Daniel Craig created a minor fashion buzz when his James Bond wore it hunting in 2012’s “Skyfall.”

“Whenever I see anybody of celebrity status in one of our jackets it’s a buzz,” Helen Barbour told BBC in 2014.

Perhaps it shouldn’t be surprising that Capitol Hill’s (and to a certain extent D.C.’s) preferred model is the Barbour signature wax jacket, given its history as a preppy status symbol.

The Jacket’s arguable D.C. heyday coincided with the peak of another: The Late Night Shots-era Georgetown and Glover Park. From 2006 to 2011 you could spot several in any bar at the corner of Wisconsin and N, what I affectionately called Brooks Brothers Crossing. At Paolo’s (RIP), Martin’s Tavern or Daily Grill, freshly waxed jackets would glare from TV screens showing college football on Saturday night.

Many elegies have been written about the demise of Georgetown as the epicenter of preppy staffer nightlife during the Bush and early Obama eras. But if you were out at Smith Point (RIP) around 2009 you would have surely encountered The Jacket. It probably just ordered a Red Bull + Vodka.

Later, you may have seen it at the Five Guys across the street before stumbling into a cab with a greasy brown bag. The Jacket takes it for granted that Alabama football will play for a national title this year but really thinks anyone coming out of the SEC can win it all. The Jacket knows every word to “Forgot About Dre.”

It’s still at Townhall but now The Jacket can be seen all over town, on U Street, in line at the Hawthorne or Franklin Hall or Wet Dog. Or in DuPont at Mission.

Grog and Tankard becomes Gin & Tonic becomes Mason Inn (RIP). Old Glory is no more. The scene may change but The Jacket remains the same. It is classic. After all, I should know.

I own two.