“I’m influenced by vintage uniforms 100 per cent,” says Oliver Spencer, who designed one of the coolest jackets I’ve seen this season: a groovy red velvet number that he based on a First World War field coat (which was originally in a sort of loden colour, obviously, not in red velvet) and which I urge you not to get because it would be a sod if we bumped into one another at a party wearing the same thing.

What’s great about military clothing, Spencer argues, is its mix of “ceremony and utilitarianism” that makes it key to the way modern men like to think about their clothes. They want something smart, with a bit of tradition behind it; but just as importantly they want it to be functional.

Much of the detailing you see on modern menswear — be it the multiplicity of pockets or the belt loops or the little press-studs, flaps or patches that probably had a purpose once but are now just there for ornament — originates from military uniforms. The Nigel Cabourn trousers I’m wearing as I write, for example, are in an Afrika Korps sand colour, made of a water-resistant cotton fabric — Ventile — designed during the war to keep ditched RAF pilots warm in a baggy shape probably inspired by the sort of thing the Fallschirmjäger wore when they parachuted on to Crete.

There’s still a bit of embarrassment in fashion circles about just how many of their design ideas are filched from Nazi kit. A few years ago it was revealed that Hugo Boss made uniforms not just for the Wehrmacht but probably the SS, too, most likely using slave labour. The company’s Italian owners were mortified and had to point out that this was a long time ago, and that anyway they were no longer a Boss family-run business. But I doubt that the revelation did their image much long-term damage: as almost everyone privately acknowledges, the Germans did have the best-looking uniforms.

I found a brilliant analysis of why this was at the website of Lost Battalions, America’s most accurate reproduction manufacturer of German Second World War uniforms. The key was the development in 1934 of the classic M36 feldbluse (field blouse), in which the sleeve cuff was shortened dramatically and the hem of the jacket skirt raised. With the belt worn high around the waist, this created the optical illusion of the German Army being full of tall Nordic supermen with trim torsos and amazingly long legs. Indeed, before it went into production, the uniform was reportedly tested on female focus groups to make sure that it generated the requisite morale-boosting increase in the soldiers’ sexual desirability.

But the Germans didn’t have the monopoly on decent-looking clothes. Our standardissue British battledress may have been thick and itchy, but our paratroopers did have the handsome Denison smock, with its button-under strap to stop it billowing during descent. US Second World War-era kit, meanwhile, from the simple khaki T-shirt and loose comfortable trousers to the MA-1 flight jacket, has pretty much decided the direction of casual dress ever since.

The GIs’ single biggest influence, though, was in the clothes that they wore off-duty. While it isn’t quite true that jeans were unknown in Europe before the war — there are early photos of Picasso in denim, for example — it was only when GIs started bringing them over en masse that they acquired the cultural dominance. “It’s a cliché but it’s true,” says Paul Trynka, author of Denim (Aurum), a cultural history of jeans. “And it’s not just that GIs spread the look to Europe. They spread it across America, too. People didn’t travel about a lot in the Thirties, but the war changed everything, causing these huge migrations. Then later, of course, that connection between jeans and the military continued because the only places you could originally get them were army and navy stores.”

Levi’s Vintage is bringing out a very handsome, limited-edition package in celebration of this, to coincide with Remembrance Sunday, with 10 per cent of each sale going to the Royal British Legion. At £300 a shot, it probably sounds rather a lot for a 1940s-style denim laundry bag, a khaki T-shirt, and some 1937 replica 501s. You might think differently, though, if you saw the quality of the replicas. Most of my favourite T-shirts are Levi’s Vintage — the cotton is of such high quality and the cut is always so right; as for the retro jeans, well, they put such effort into the detailing, and the wash, that it’s like unearthing the real thing from your long-lost American great-great uncle’s drawers.

Mind you, if you’ve that sort of money to spare, you might just as well go for the real thing. It wouldn’t buy you a pair of original 1937 501s but would buy you some genuine Second World War kit, provided you knew where to look. One of the best places over here is What Comes Around Goes Around? in Camden Market, North London. Better still, there’s the Puces de Paris-Saint-Ouen flea market in Clignancourt, where there are specialists who track down the rarest and finest war uniforms. Of course, they’ll have been snapped up by the time you get there. Yohji Yamamoto, or Nigel Cabourn, or Paul Smith, or someone will have got there first.

The Levi’s bags are available exclusively at Cinch, 5 Newburgh Street, London W1.

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