One Direction

The problem with the British economy, we are so often told, is that we're over-reliant on the service sector. We just don't make things any more. But judging from tonight's gig by One Direction, at least one of our traditional manufacturing industries remains in fine fettle, employing cadres of people and exporting hand over fist: manufactured pop.

Just over a year ago, One Direction were setting off on a regional tour, supporting their debut album, Up All Night. They were coltish and gawky, gamely braving matinees packed with overexcited girls in medium-sized halls where the seating moves back. Their fortunes, frankly, could have gone in either of two directions.

Eschewing dance routines and R&B, focusing instead on fashion "scenarios" redolent of a Jack Wills catalogue, 1D were a novel thing – a boyband aggressively styled as middle class. It was a gamble. There were (as far as I can tell) no formative tours of gay clubs, the traditional supplementary market for popular male vocal groups. One Direction came straight off the telly – five X Factor entrants glued by hair gel into a 10-legged teen-girl dream – and into your town.

Their pop was old-school, too, like Girls Aloud's: it had roustabout rhythms rather than breakbeats, and apart from Zayn Malik posing behind decks and the odd synth stab it was relatively free of the influence of rave culture, now dominating even R&B. This gambit worked well for Girls Aloud a decade ago, setting them apart from the prevalent sounds of their time, and it's working a treat for 1D now. In 2012 their two albums – Up All Night and its follow-up, Take Me Home, released at the end of the year – were the fourth and fifth biggest-selling albums worldwide. They are more wanted than their rivals the Wanted, the notional "bad boys" of the boyband market, managed by Scooter Braun, Justin Bieber's svengali.

Tonight, over the course of one-and-a-half hours and 21 songs, culled from two albums and an execrable charity cover version medley (One Way or Another by Blondie into Teenage Kicks by the Undertones), not one beat implies any sort of attitude, not one note sounds any kind of threat. It's all fun, fun, fun – the Monkees pushing the Beach Boys into a swimming pool – and romantic yearning.

 You could spin the 1D shtick in two directions. Either it's a cultural calamity, in which yet another generation of young women is served a nutritionally poor diet of McMusic laced with lies about intergender relations. Or, alternatively, One Direction provide a welcome breathing space from the rampant pornification of everything, confirming the existence of romantic love and peddling a kind of comforting, worry-free Britishness in the face of a rapidly changing reality. I veer from one view to the other and back again over the course of the gig.

A year and a bit on, Harry, Zayn, Louis, Liam and Niall remain coltish, frolicking around the O2 stage where Take That would have been drilled into formation bum wiggles. But their mic-handling skills and notionally offhand gestures are now thoroughly professional.

Since the start of the tour last month, they seem to have cut out the costume changes. They still don't dance – this is One Direction's defining USP, other than dressing like a catalogue – but they can all (sort of) rub their bellies while patting their heads, as per a question sent via Twitter. The 'D take more Twitter questions while marooned on a mini-stage mid-venue, having been airlifted there on a mobile platform – the one bit of woo-woo stagecraft they've invested in for this maiden world tour.

Two key things have changed for ever. Tattoos have crept across One Direction's previously flawless young flesh like an oil slick. Liam, for one, seems to have go-slow traffic chevrons on his arms, which some outposts of girlkind assume to be arrows, going in one direction.

The other is America. Early in 2012, Up All Night came out in the States, going to No 1 immediately. No other British band has achieved this on their debut. Traditionally, the US has remained largely immune to the charms of the Anglo-Irish boyband phenomenon; it was ours alone. One of the reasons Robbie Williams moved to LA in the early 2000s was that he could walk about unmolested.

But now 1D join Adele and Mumford & Sons as limey cultural commodities Americans can't resist. The inclusion of red phone boxes and other Brit-kitsch in their artwork is no accident. Unlike the Mumfords, though, 1D songs tend to be written by the same international cabal of two dozen people who write most pop music, here, there and everywhere.

Thanks to that giant echo chamber, tonight the melody of I Would sounds ever so slightly like a melody from Drake and Rihanna's Take Care. Remarkably, Over Again – one of two contributions to Take Me Home by Ed Sheeran – stands out starkly from the rest of their songs, in that it contains some vestiges of personality in its craven, glowsticks-aloft balladry.

As for the world tour – Europe next month, the US all summer – you wonder idly why they are bothering, as the talk in the long queue for the ladies is all in Dutch and Spanish; Niall points out an Argentinian flag in the crowd. And try as they might to keep things clean, sex keeps coming into it, creating a dilemma for their third, as yet unwritten album: stick to the no-thrust formula that has been so successful thus far or lose their innocence, just as so many of their followers are thinking of losing theirs?

Because when the members of One Direction lower their microphones to their groins and strum them like guitars tonight, it doesn't look like they're strumming microphones like guitars. It looks like they're doing something quite different.