In just two years, since coming third on X Factor, they’ve charged their way to global fame, smashed new records and set millions of hearts aflutter. Not bad for a boy band who don’t dance. Jo Ellison tries to catch up with One Direction in the December issue of Vogue.

Could it be that the only person in the world not familiar with One Direction is Patrick Demarchelier, the photographer today charged with capturing the fab five for Vogue. Sitting on a battered leather sofa in a comfortable studio in north London, his typical Gallic indifference to the upcoming task is almost comic. “So, oo iz ziss zat we are shooting?” he appeals to the room. “The Beatles?” Pretty much, an entourage of overexcited females nod back. He shrugs, and glances at his watch.

For the benefit of Demarchelier – or those who don’t associate regularly with seven-year-olds, televisions or radios, or those of us of a slightly older vintage with dubious moral intentions – One Direction are currently the biggest pop band in the world. In two years, since coming third in the reality talent factory X Factor, they have achieved successes even Simon Cowell couldn’t have quite dreamt of. At the time of writing, Messrs Liam Payne, Harry Styles, Zayn Malik, Louis Tomlinson and Niall Horan are number one in 50 countries, boast about 10 million Facebook fans and lead more than 6.5 million followers on Twitter. Their debut album, Up All Night (a pop-pourri of infinitely familiar but earwormy tracks, including the ubiquitous summer anthem What Makes You Beautiful), was the first by a British act to go straight to number one in America. Ever. Its release coincided with an epic, global, sellout tour, during which their every movement was accompanied by a shrieking tsunami of tweenage desire. They’ve just recorded a “difficult” second album in Sweden.

Critics may dispute their musical legitimacy – they don’t write songs, nor play instruments, nor dance (unless you count swaying vigorously on the spot). Neither was their genesis remotely organic; the five were thrown together “live” on air when they failed to persuade the X Factor judges of their strength as soloists. In short, they are as manufactured as McDonald’s. But 1D, as their apparently un-ironic moniker would now have them, are the modern pop phenomenon. As Alexa Chung puts it: “They’re no Beatles, obviously, but it’s nice to see a boy band dress well for a change. They remind me of a box of puppies at Christmas – each one more adorable than the next.”

The question as to exactly who is the most adorable remains the most hotly contested debate in the playground today. Is it Liam, from Wolverhampton, star sign Virgo, with his newly shorn, post break-up crew cut, his phobia of spoons and his excellent Kermit the Frog impression? Or Zayn, a chocolate-eyed Capricorn from Bradford, who has three sisters, always wears two pairs of socks and can’t swim? Maybe it’s Louis, the green-eyed granddaddy of the gang, another Capricorn, this time from Doncaster, about to turn 21 and one of only two members to hold a driving licence. Is it little Niall, Virgo, a blond moppet from Mullingar in Ireland, with not-so-invisible invisible braces, “a soft spot for girls with green eyes” and a habit of curling up and dozing off at any given opportunity?

Or is it Harry? Which, of course, it is, because if you have heard nothing whatsoever of One Direction you have probably heard of Harry Styles, the hazel-eyed, mop-topped, bedimpled lead singer and baby of the group, with whom the whole world has fallen in love. Harry, an Aquarian, who hails from the village of Holmes Chapel in Cheshire. Harry, whose delightful scowl of petulant confusion, like a teddy bear trying to do trigonometry, has skewered millions of fluttering hearts, and has wooed scores of women if the papers are to be believed (and wouldn’t you, if you were he and had that kind of opportunity?). Harry, whose favourite food is tacos, who hates mayonnaise, adores the Beatles, likes to perform Justin Bieber at karaoke and who is the first to introduce himself to the assembled crew when the band arrive, two hours earlier than scheduled, throwing everyone into a paroxysm of panic that even the best Carry On film couldn’t emulate.

“You’re never going to get used to walking into a room and have people screaming at you,” he says of his status as World’s Most Fanciable Adolescent, as a stylist fumbles around him with a black tie in as professional a manner as she can muster. Despite being so terribly attractive, with his lazy northern brogue and cursedly pretty face, he has managed to stay sanguine about his fame. “There’s a lot of things that come with the life you could get lost in,” he says, eyes flickering earnestly under the signature ‘do (ebony curls, fringe swept-over, mussy at the back). “But you have to let it be what it is. I’ve learnt not to take everything too seriously.”

And how does he feel about the endless photocalls and press shoots that go with the territory? Days like today, for example. “I enjoy ’em, actually,” he says. “Especially ones like this, where you don’t have to just sit there and grin.”

He’s especially comfortable in the fashion world; he was the only member of the band who sat front row at Burberry last September, for example. “I like fashion,” he says. “When I look back at the kind of stuff I wore on the X Factor, I laff.” In fairness, he was only 16 then, a highly forgettable period in anyone’s style evolution. “No,” he shudders, recalling the bow ties and long straggly scarves that accessorised his earliest television appearances. “There’s no excuse.”

Despite being the most obviously charming of the group, Harry is also remarkably self-contained. In front of the camera he can appear removed, even shy at times. As to his role in the group: “I float a bit,” he says vaguely, before adding, “and I can fall asleep anywhere. That’s my thing.”

Asked to identify the “father figure” among them, the boys nominate Liam, who is wrestling with the laces on a new pair of white Converse and getting used to the aforementioned haircut. “At the start, the management said I wasn’t allowed to change my hair,” he says of the strict aesthetic with which the boys are expected to comply. “But then I did it anyway, so they kind of let that one go. I tend to change my hair quite a lot.” The change affords him a small window of anonymity. “I can go out and about,” he says. “The other day I went out dressed as a big chav – Adidas trainers, jogging bottoms – and no one recognised me.”

“It seems almost sad that a little haircut should represent such a big opportunity for the boys to lead anything like a normal life, if only until the papers catch up with them 24 hours later, but they are, at least, beginning to enjoy more autonomy in their artistic lives. The new album allowed them “to experiment with new sounds”, says Harry. “We want to gradually get more and more ‘live’ sounding. So this album is a lot less little synth sounds, more guitars and drums. It’s important to experiment with things – we want to move with the times, but keep true to ourselves.”

I love the screaming.

For others, the second album was a longed-for chance to flex some musical muscle. “We did a lot of writing in the studio,” says Niall, the self-described “carefree” member of the team. “And I play the guitar, so I play on a lot of the tracks on the album.” A “born performer”, whose first party trick, aged four, was to sing Saturday Night at the Movies to any willing audience, Niall has no issue with screaming women. Adores touring. “I love it. I love the screaming. They love it, too: they’ve all got their tickets and they’ve been waiting a year or so to see you, so you’ve got to give it your best.” That said, he – like all of them – is looking forward to the three-day holiday they’ve been allocated, and the quiet normalcy of “hanging out at home and going to the pub with my old mates”.

But now it’s time for work. And so they assemble, staring down the lens of Demarchelier’s camera with all the intensity of Derek Zoolander, as the sphinx-like Edie Campbell trails lissom limbs along their shoulders. Approaching 22 herself, she’s far too old for these young swains: “They’re just children,” she laughs as she quick-changes into white Dior. Anyway, the boys seem largely impervious to her beauty, Zayn standing stock-still as she arranges herself around him, never breaking eye-contact with the lens. Perhaps he’s in awe of her – the band’s groomer later mentions she’s never seen the boys so “well-behaved”. True enough, they are a treat to shoot: quick, uncomplaining, each doing just as they are told – there’s barely even any banter between frames. It’s far from the hi-energy performance they bring to the stage, but no less efficient.

Such professionalism is almost eerie – the product of a long, long education at the school of Simon Cowell but they’re ever so sweet with it, too. Afterwards they sign autographs, pose for pictures, thank everyone for their time, and are as lovely as you hope they’d be. And then they’re off, all ushered, in one direction, towards the next appointment on that relentless schedule of world domination.