The sartorial evolution of Andy Burnham reached another milestone this week when the prime minister appeared at a photocall in Derbyshire wearing a pair of braces under his suit.

Navy, slimline and button-on rather than clipped, they were barely visible while he posed for a photo in Ilkeston. It was only when he unbuttoned his suit jacket to embrace members of the public that they were on view.

Burnham’s £595 navy suit was made by Oliver Brown, a traditional tailor with shops in London and Chester, and is the same style worn in his official portrait. Called the Eaton suit, it is made from a 100% merino wool cloth woven by Alfred Brown in Yorkshire, and is made to measure. A spokesperson for the tailor said that while the suit was definitely theirs, the braces were not.

If the trousers didn’t fit, wearing a belt would have been out of the question as they don’t have belt loops. And yet, says Chloe Chapin, a fashion historian and author of the forthcoming book Suitable: The Sartorial Revolution and the Fashioning of Modern Men, “the trousers do have side fasteners, so he doesn’t really need braces at all, at least functionally”.

A political insider who has worked on Burnham’s campaigns for the last two years told the Guardian: “Andy is not the teleprompter type of politician. This stuff is simply what he wears.” The former Greater Manchester mayor and his team think about his clothing and context, though, and it certainly isn’t an afterthought. “His clothes are trying to strike a balance between professional and capable politician – but also let people know that he’s different to other politicians,” the source says. As the first TikTok PM, no one understands this better than Burnham. “The optics are not divorced from the reality”.

Braces originated in France in the 1700s as strips of fabric that were buttoned to a waistband. They quickly spread across Europe, like many French trends, though it wasn’t until 1820 that Albert Thurston started making the leather versions we know today. Back then, they were considered undergarments and to show them was inappropriate.

Braces had a resurgence in the UK during the 1960s and 70s, worn by mods and skinheads as a form of subversion. The pinnacle of this probably occurred in the 80s, when they became as popular on Wall Street financiers as they did on punks. Wearing this “underwear as outerwear intentionally was a bit like Madonna wearing her Jean Paul Gaultier cone bra, a real statement”, says Chapin. If the 60s version represented working-class pride and anti-establishment rebellion, the 80s “was about a heightening of excess. They transcended class and in an age of abundance showed just how subversive fashion could be.”

While Burnham has always been transparent about his journey from Westminster yes-man to “king of the north”, particularly through his wardrobe, could the braces signal a move to formality? In many ways they are the ultimate symbol of tradition, especially in politics, where Winston Churchill and Michael Portillo were fans.

It’s more about context, says Chapin. Just as a Labour politician will wear red if they want to convey strength, grey or purple if they want to be bipartisan, or blue if they’re talking to Tory voters, if something can be both posh and working class at the same time, this is precisely the sort of ambiguity a politician might want to exploit if they’re trying to connect with the public.

If nothing else, Burnham wearing braces points towards fashion’s core tension – is clothing about function or aesthetics? Much like his approach to politics, the answer is probably both.