Some men look good in a suit. Others struggle. Never was this line more squarely drawn than when the 58-year-old actor Brad Pitt, and the 58-year-old outgoing prime minister, Boris Johnson, wore baggy linen suits to drastically different effect over the past week.

You might have glimpsed Johnson’s cream linen suit, paired with a sky-blue shirt, when a leaked video of his late July wedding party in the Cotswolds appeared online. Too long in the leg, and so generously sized it bordered on cartoonish, it was quintessential Johnson, proof that for the select few, deliberate scruffiness is not simply a privilege but a must, even on your own wedding day.

By contrast, Pitt’s suits worn during the promotional tour for his new film Bullet Train have broken large corners of the internet. Equally creased and generously sized, they came in zippy shades of zoomer green, cantaloupe granita and burnt espresso, and were designed by the slow-fashion Dutch designer Haans Nicholas Mott. One even came with a skirt. When asked by Variety why he was wearing what he was wearing – as is red-carpet tradition – Pitt alluded to climate breakdown: “I don’t know! We’re all going to die, so let’s mess it up.”

All of which begs the question – is Johnson suddenly fashionable, or is Pitt suddenly not?

Blame the weather, but the large linen suit has become standard issue for men entering a new phase of life and, when done well, it can be “an exciting evolution” says the fashion writer, editor and academic Dal Chodha. “Dressing in linens, slow fashion, things that are in between skirt and trouser, menswear and womenswear, is right for the times,” he says, likening Pitt’s red-carpet moments to Harry Styles appearing in a dress on the cover of Vogue in 2019, or, in 1998, David Beckham wearing a sarong over trousers, in their cultural cachet.

Chodha, himself a fan of a looser silhouette (“I don’t want to feel a seam cutting into me – I don’t want my clothes to police me if I put on a bit of weight”) thinks this “rebranding” of Pitt is a wholesale success, a deliberate “softening up of what ‘menswear’ can mean” and “a much more poetically virile swoop into middle-age” than Johnson.

The fashion psychologist Carolyn Mair agrees: “I doubt that Johnson’s reasons for choosing baggy over fitted or tailored were to do with style.” Rather, she says, it’s “simply his brand”.

Silhouettes tend to expand during boom times – see Dior’s postwar tailoring (dubbed the New Look) and the billowing shapes of Armani’s late 90s suits. The same could be said of changes, such as the end of a career, and this sort of look – loud, louche, fun – could be considered a “retirement suit”. Johnson, as we know, already has one foot out the door. And as Pitt told GQ of his career, “I consider myself on my last leg … this last semester or trimester.”

Mair says: “At times of separation, we might prefer to either remain ‘hidden’ or take up more space, so they’re choosing baggy clothes that take up more room, making the wearer seem larger than they are and emphasising their presence.”

From the Delhi-based label Itoh to M&S and the British labels SMR Days and Oliver Spencer, the “loose linen look” has gained wider currency among men who don’t know what to wear when it’s hot but perhaps have the means or the need, such as a ticketed event, to dress up anyway. That Johnson’s aesthetic is closer to that of advertising’s late Man from Del Monte (the actor in question, Brian Jackson, died last month) suggests that, mentally, he is already in even sunnier climes than Britain’s.

But with Covid, relaxed dress codes – and heatwaves – putting paid to suits, the linen look is likely to linger. The tailor Oliver Spencer calls it “the suit of the future” – or for people who don’t normally wear suits. “They are very easy to wear. [The wearer] gets to dress up without feeling ‘locked up’.” Loose linen suits have become bread and butterfor British tailors, and along with seersucker outfits, continue to outsell everything else during summer.

Chodha nevertheless thinks men should approach this look with caution. “The worst thing that can happen now is if the middle-aged men of the UK, inspired by Brad, descend to their drinking holes in linen skirts.”