Justin time

The girls have the building surrounded, deployed in a perimeter formation so thorough you imagine a veteran Swat man taking a glance at their positions and giving an approving thumb.

On the north side of the stadium - Pauley Pavilion in Los Angeles, which in a few hours' will host the Nickelodeon Kids' Choice awards, an annual celebration of America's celebrity teenagers - a phalanx of young fans, mostly female, aged mostly 10 to 15, has gathered around a cordoned-off fire door rumoured to be a secret entrance or exit for VIPs. Others are stationed in clusters as close as they can get to a giant white marquee that (a bouncer has let slip) will host the after-party.

Dedicated, professional, at least 100 of them have also taken up post in an underground car park, risking it all on a rumour that this is where the object of their ardour will be dropped off.

Most are playing it safe, lining up above ground along a slip road to the south of the stadium where the limousines are due. Here, the volume of young fans is growing so rapidly that a yellow-shirted security guard has to keep walking away, grumbling, to fetch more lengths of crush barrier. Whenever he lopes off, a girl at the front of the crowd shouts: "Are you going to bring us Justin?" The guard gets no chance to reply; the mere utterance of this particular name sets off a series of murder-screams in the pack behind the girl. It will be a long afternoon for the guard.

The girls are waiting for Justin Bieber - "Justin Baaaaargh!" as it sounds when howled in hysterical chorus - the mop-topped 16-year-old is currently one of the most famous musicians in America. He is part R 'n' B crooner, part rapper, part "ooh baby" popstrel - all beardlessly, brilliantly charming to girls of a certain age. Bieber can no longer walk in the open without being mobbed, nor make public appearances without ambulances present.

It started four years ago when Bieber, then a precocious pre-teen in small-town Canada, uploaded footage of himself to YouTube, warbling cover versions of songs by Usher and Chris Brown. Bieber had something, that nebulous x-factor - a decent voice, a bit of sass - and his page started to draw its first fans, web-browsing "tweens" who emailed back and forth the links to his cutesy cover renditions. Then footage of Bieber was spotted by music impresario Scott Braun, who'd been scouring YouTube for a "different" young hopeful and had clicked on a "related link" that led him to Bieber by accident.

Braun made contact and eventually signed Bieber up, relocating him and single mother Pattie to Atlanta to start the process of moulding the youngster into a pop star: the voice coach, the studio sessions, the obligatory patronage of a torch-passing older artist (Usher), even the employment of an official "swagger coach" to help spin Bieber's sass into charm and refine his appearance with nifty T-shirts, chunky trainers and bling.

All pretty cynical, all (one imagines) pretty standard in the pop business. But Bieber's team made the critical decision not to neglect the original YouTube fans, nor remove Bieber from sight while he was groomed for his new career. Instead, they continued to drip-feed regular, unglitzy footage to his YouTube page, clips of Bieber singing or plucking at a guitar or horsing around. His fan base grew and by the time Bieber - now a teenager, newly groomed, with added swagger - released his first single in the middle of 2009, he had a preposterously large internet following of around 40 million fans. It meant that all seven of the songs on his debut album, My World, charted in the US - a record - and by December he was performing for President Obama in Washington.

Where once pop artists would stagger their releases, My Worlds, an extended version of the original album - a bit more production on the old tracks, plus a few new ones - was released last week. It debuted at No 1 on the Billboard 200 albums chart, making Bieber the youngest solo male artist to hit the top spot since Stevie Wonder in 1963 (with Little Stevie Wonder/The 12-Year Old Genius).

"His fans have a vested interest in him because they saw him before the music videos and the glitz, just as a singer in his house," explains that swagger coach, Ryan Good. "He's his own little sensation," says Steve Bartels, the president of Bieber's label, Island Records. "He had no platform." And a "platform", in recent years, has been essential in fashioning new pop acts this big.

Megastar teens Miley Cyrus and the Jonas Brothers were launched skywards by their own TV shows on the Disney Channel. Contestants on American Idol and the cast of High School Musical likewise get plonked in the homes of millions, their careers kick-started accordingly. Bieber's success, based primarily on a lot of grainy clips of himself mugging for a camera, must have a lot of executives wondering why they've spent so much money. They could've just given Miley and the Jonases a cheap webcam and free rein.

"He started talking to the fans, being honest with them, and it just multiplied from there," says Bartels.

"He went viral," says Good.

"His success almost seems like a reaction against High School Musical," according to Peter Robinson, editor of Popjustice. "That was a brand in which music was integral but also seemed downgraded to being just one of a thousand revenue streams somewhere in between lunchboxes and stationery sets. Bieber's own route - from YouTube straight to an audience with Usher - was something more anarchic."

Is that what the fans think? Sarah, 12, from Victorville, one of the earliest to arrive at the cordon outside Pauley Pavilion, has been hopping from foot to foot in expectation of a sighting. Why does she like Bieber? "Because he's cute and he has great songs and I love him playing the guitar and he's cute." Andrea, 11, from Whittier, has a go: "He seems like more fun than the others and he's a great singer and his lyrics make sense and he loves us and" - she can't resist - "he's really cute". Where did they first hear about him? "YouTube," they say in unison. "I sent the link to her," says Sarah. "I sent the link to her," corrects Andrea.

The traditional barriers between a megastar and the anonymous girl who follows his adventures from afar have been eroded by Team Bieber's canny understanding of its market: kids with an internet connection, just about savvy enough to be suspicious of corporate pop.

Bieber, his fans believe, offers something more homespun. "He doesn't represent anything staggeringly new," says Robinson, "but he's been something this generation can get excited about and call its own." Or as Bieber's manager Braun defined it in an interview last year: "We'll give it to the kids, let them do the work, so that they'll feel like it's theirs."

It is now the early afternoon and the security guard bossing Sarah and Andrea and the hordes of fans at the entrance to Pauley Pavilion is learning something new about the screams of star-stricken girls. What may once have sounded to him like a single, universal noise - a shrill generic note, pitched roughly above the squealing car brake but below the dog whistle - is proving to have a greater deal of subtlety.

An entry-level scream, a kind of fierce "yay!", is unleashed when the guests who step from the limos are recognisable but too old - sorry Katy Perry - to count for much to this particular crowd. Then there is a scream above in its ferocity, a triple-dash blast that could almost be an attempt at Morse code, and has probably evolved from the girls' attempts to shout: "Oh my God!" while simultaneously opening the mouths to the full for a giant wail; that scream is for the next strata of young celebrity, Will Smith's son, Jaden, or Taylor Lautner, the werewolf from Twilight, for instance.

Comedian George Lopez and chubby actor Jonah Hill get a half-hearted yelp of their names, but the real noise is reserved for Bieber. His seems the ultimate level of scream, a quick breath and shriek that must surely represent the upper limit of human noise (anything more and the larynx would rupture, surely, the lungs explode).

This scream, the Bieber scream, is getting many practice runs at Pauley Pavilion. Teenage boys keep stepping from limos with deceptively similar hair, in similar chunky trainers, briefly tricking the crowd into thinking that he is here. But the start of the awards show is fast approaching, and still Bieber has not appeared. "He's not even tweeting," says one despairing girl, checking her phone for updates. "He always tweets."

Bieber does always tweet, another way that he exerts an almost hypnotic sway over this crowd. Mostly it is harmless cheerleading - "3 yrs ago i started a youtube page in my lil town of 30k people [and now] I am living my dream".

Why? The fans - plus the singling out of individual girls who've tweeted for his attention. But Bieber also hard-sells to them like a veteran huckster ("Let's go for number-one buyouts at every store ... get your friends and let's do it!") and sends out rallying calls ahead of his public appearances, something that has caused problems. Last year, the announcement of an autograph session at a mall in Long Island lured so many thousands that, according to the New York district attorney in a later inquiry, security rails and shop windows buckled under the weight of bodies.

In fact, in what surely must be a legal first, Braun was brought before a judge on March 26, charged with not tweeting in time to tell fans the event had been cancelled. The case is still to be resolved, though Bieber has offered unqualified support, promptly updating his Facebook status after the arrest with the message: "Free Scooter Braun, support you 100 per cent." Within the hour, he'd also posted: "What is your favourite song on My World 2.0???"

Is it always, as the fans believe, Bieber posting these messages? Or is there a shadowy communications team, sitting in a bunker somewhere with spreadsheets and focus group findings, working out the perfect status update or 140-character message to feed the fervour?

Two days after the stakeout at the Nickelodeon awards, I get a chance to ask when I meet Bieber on the set of his new music video, filmed off Sunset Boulevard in Los Angeles.

In person, his size is a bit of a surprise: after several hours staked out with his fans, I had in mind a giant. But Bieber is about 1.63m, maybe just under - child-size, appropriately enough, though wearing over-size shoes and jeans that make him look oddly bottom-heavy.

His hair helps redress the balance, an immaculate arrangement of straight sandy blond, much commented on by fans and detractors, that sweeps around and forward and frames his face a bit like a balaclava. He has no spots - perhaps they've been and gone or have still yet to come. His braces, I have read, are special invisible ones, installed by the orthodontist mother of his manager.

There is a mobile phone clasped in his hand. Is it always him tweeting and editing his Facebook page? Bieber nods. "I keep it all on here, it's all on my iPhone. I enjoy updating my status. Tweets and stuff."

Hyperactive, he could be mistaken for hyper-cocky, too, but when we settle down to speak in his trailer he has perfect manners. He has already told me, in a quick blast of getting-to-know-you japery, that his name is Rob, that I look like Napoleon Dynamite, and that he likes football, calls it football, not soccer, and supports Chelsea, though he knows Chelsea lost the other day and that they never normally lose.

I am hopeful that my allotted and rather limited interview time will all be pretty zingy, like this. But Bieber has been interviewed many, many times in recent months - by David Letterman, the New York Times, Ellen DeGeneres, Billboard magazine, with only really Oprah left to tick off the list - and he is quickly, politely, bored. Besides, somebody has parked a yellow Lamborghini near his trailer and there are a dozen colourfully clad teenage girls milling around as extras for the video shoot. Ours is a distracted exchange.

Has his burgeoning career been hard work? "It's been pretty crazy." Does he expect it to get easier? "It doesn't really get easier or harder." Who does he look up to? "Usher. He's who I want to model my career on." Where would he be now if he'd never uploaded a video of himself to YouTube?

"Probably at home, chilling." Is he ever unnerved by this new constant in his life - the wailing teenage scream that accompanies his every appearance in public? "I don't really get nervous. Ever since I was little I've liked being the centre of attention."

There is a brief moment of panic when he jokes that Canada, his home nation, is "better" than America - a glance to his bodyguard, present throughout, to make sure he hasn't boobed. But otherwise he is unflappable. Where does he think he'll be in five years' time? "Making albums," he says. Maybe "in college, that's definitely something I'd like to do". At the very least he'll have "been on Oprah".

Then he is off, rapping to himself about cars and American football and (it seems almost cruel to mention) "Justin Bieber fever". Outside, he fiddles with the window of the Lamborghini and high-fives a few of the teenage extras, before bounding away to the set. A substantial entourage follows in his wake: there's the bodyguard, vocal coach and home tutor; also a "surrogate mum", a friend of Bieber's mother who is back at their hotel sleeping off jetlag.

"He's great to work with," says the vocal coach. "He's a lovely kid," says the home tutor. "A talented dude," surmises Good, "with a personality the size of the world." It all seems fair.

However abrupt my encounter with Bieber, I got closer to him than most of the fans who'd staked out Pauley Pavilion on Saturday afternoon.

Those at the front of the building found out that he'd been inside the building all day, rehearsing a live performance; those in the car park had gambled and missed out. All went home disappointed. Only the crafty fans who camped out by the stage door got lucky.

Here, where two rows of crush barriers had been set up to ferry VIP guests from stadium to after-party marquee, one or other of the well-researched fans spotted Bieber's bodyguard milling around. Those who got word in time came at a sprint; a chant of: "We want Justin" grew louder and suddenly, as if in answer, he was there.

Whoosh: the Bieber scream, unleashed at full force. It physically hurts, that noise, digging into your ears like a sharp stick, but Bieber strolled through, unruffled. He waved one way, gave a peace sign the other, and then was hurried on by his guards, everybody mindful of what might happen if he stayed longer: the ambulances, the district attorneys, another Long Island.

In 30 seconds, he was gone. The screams lasted longer. "I saw Justin Bieber," said a girl wearing braces, swaying away from the barrier. Her eyes were squeezed shut. She seemed to be trying to preserve the image.

"I got some pretty loud screams," Bieber will say later. "I don't know why. You'd have to ask them. I don't know what about me they like. But I'm glad they do."

- OBSERVER

LOWDOWN

Who: Justin Bieber, 16-year-old Canadian pop sensation, heart-throb and protege of R 'n' B smoothie Usher.
What: In New Zealand on April 28 for a promotional visit.
Debut album: My Worlds, out now.
Also: The 23rd US Nickelodeon Kids' Choice Awards screens in New Zealand on Saturday April 17, 8pm (Sky channel 41) preceded by Kimberley Crossman's Orange Carpet Pre-Show, 7.35pm. Repeat screenings follow on Sunday 18 (8.40am and 9.05am; 5.40pm and 6.05pm) and Monday April 19 (4.05pm and 4.30pm)