Of all the photographs showcasing King Charles III’s personal style – that cascade of double-breasted frontage, oyster-cream safari suits and frankly intimate jodhpurs – one lodges firmly in my mind, like a signet ring embedded forever in the grooves of a royal pinky. 

It was taken on 1 July 1990, outside Cirencester Hospital. The prince can be seen emerging from the ward with his arm hung louchely in a sling, the victim of a particularly robust polo chukka. His wrist is swollen and bandaged; the precise prognosis is unclear. But the general elegance is never in doubt. Those pale stone trousers, with their continental pleats, starched defiantly against the heat of the late afternoon. That midnight-blue blazer hung jauntily off one shoulder in the manner of an Italian count. The pale blue shirt, opened to a three-button salute, one collar-tip poking gamely out from the blazer’s peak lapel… 

And that sling – the sling! – hung in a perfect V around the neck like an open cravat, its shade of Hermès-grade pink matching perfectly with the chintzy flowers of Diana’s skirt, just next door. (The injury took place on the princess’s birthday, by the way, and her perfect look of amused, chiding indulgence is a statement of style in itself.) You’d call the whole thing sprezzatura (that knack of making a whole lot of sartorial effort seem utterly effortless), if it wasn’t so damned English. Anyone can look stylish at a planned photo op, but it takes a king to look this good by accident. 

Not that there are many accidents when it comes to Charles’s personal style, of course. One of the more notable rumours about this deeply discerning man’s dressing regimen is that he asks his valet to steam-iron his shoelaces each morning. Whether it’s true or not doesn’t particularly matter: Some myths ring true even when (or perhaps especially because) they simply must be false. And some details just sit right. And if there’s one thing Charles is particular about, it’s the details. 

When actor Josh O’Connor was studying the King ahead of his star turn in the third and fourth seasons of The Crown, the actor noticed a particular tick. “Whenever he gets out of a car, he checks his cufflinks, checks his pocket and then waves. The same movement every time.” This, one feels, is the sartorial equivalent of a pre-flight check; akin to the inventory commandos take before entering hostile territory. 

No matter what an engagement might throw at him – mewling babies, egg-wielding republicans, the Daily Mail – Charles knows he can fall back on his personal style for protection, for succour, for a reminder of what he stands for. In this way, the double-breasted suit is also a suit of armour – steadfast, confident, unflinching.

Continuity, you see, is at the heart of Charles’s personal style. In the avant-garde, ever-churning theatre of fashion, this is not a particularly sexy word. But, as the longest-waiting heir to the throne in history, our new King operates at a different time signature to the rest of us, who scrabble desperately over trends and fads and ‘drops’. 

He told the fashion world as much, in fact, at the launch of the (now long-defunct) bi-annual gathering called ‘London Collections: Men’, back in 2012. “I have lurched from being the best-dressed man to being the worst-dressed man,” he told the room. “Meanwhile, I have gone on – like a stopped clock – and my time comes around every 25 years.” 

This self-deprecation is supremely princely, but the truth to Charles’s stylish allure is that the earthly, mundane strictures of ‘best-dressed’ lists simply don’t apply to him. Too meritocratic, for one thing. This is a hereditary monarchy of taste; style by divine right. And it is likewise suspended from the normal rules; from the ebbs and flows of changing tastes and customs.

A laundry list of Charles’s wardrobe staples reads the same now as it would have done 50 years ago. Almost literally, actually – Charles is said to have worn the same swoopily double-breasted dinner jacket for more than three decades, while one of his overcoats belonged to his grandfather, King George VI.

His suits come courtesy of Britain’s tailoring titans: Anderson & Sheppard, Gieves & Hawkes, Ede & Ravenscroft and Benson & Clegg (on Sloane Street, the best suits are at Hackett, Tom Ford, Giorgio Armani and Dior). His shirts are almost always from Turnbull & Asser, an outfitter he shares with that other timeless British style icon, James Bond. Cashmere garments are from Johnstons of Elgin (which you can find in Harvey Nichols); Burberry does his macs and Barbour (who else?) his wax jackets (they’re available in Peter Jones). The shoes come via Crockett & Jones, John Lobb, and sometimes Tricker’s. These he prefers old and reliable, their war-story scuffs buffed out and burnished; invisible but felt. (One pair is hewn from leather salvaged from an 18th-century shipwreck in Plymouth Sound.) His morning suit has long been an almost risqué grey-on-grey ensemble – finished off by a two-tone, Gordon Gekko shirt – known as ‘pick-and-pick’. The King pulls it off, but you shouldn’t try.

Somehow, this unflinching consistency is never boring. Again, the devil is in the details. Charles, who is said to change suits up to five times a day, supported by a small platoon of valets, clearly rejoices in the subtle, personal variations available to him – not least when the palette must adapt for different cultures or warmer climes. The King’s pale 1970s safari suits – tailored closely to his rakish frame and worn in the heat of Africa or Asia – are part-Field Marshal, part-international playboy. A visit to Canada in the late 1970s yielded a peach-coloured rancher’s suit, bone-white cowboy hat and bolo tie – all tailored and finished with a millimetric precision that says ‘Windsor goes West.’ 

Just after a polo match, meanwhile, rosy-cheeked and windswept, his hands on his waist or a beer in his hand, Charles is the high priest of prep – a Slim Aarons fever-dream; Ralph Lauren regality – his chambray collar emerging below a jolly yellow ‘Happy Hermès’ sweatshirt; a polo shirt as green as the Gordonstoun outfield. Even the way he stuffs his hands in the pockets of his endless succession of double-breasted suits (there are said to be hundreds) is a statement of personal style: it is somehow levelling but withdrawn; clubby and debonair. 

On 6 May, Charles will be officially crowned ruler of the United Kingdom and its Commonwealth, in a ceremony that has been pared back and slimmed down for modern times. (It is telling that former Apple maven Jony Ive – better known for designing sleek, timeless, modernist products – was tasked with creating the ceremony’s official logo.) On that morning, Charles will become the oldest monarch ever to ascend to the British throne. Perhaps it is worth declaring him its most stylish, too.

Joseph Bullmore is a London-based writer who has contributed to Tatler and The Spectator. He is the editor of Gentleman’s Journal and editor-at-large at Air Mail.