One Direction disarm Super Size director Spurlock

One Direction wanted fans to see the 'real' them and not just the celebrity image, says director Morgan Spurlock

They are the world's biggest pop band, who became famous because of a reality TV show, and are signed to the record label of a media mogul with a reputation for control. He is a maverick film director famous for thumbing his nose at big corporations. So why have One Direction and Morgan Spurlock teamed up together?

The 42-year-old documentarian, who was nominated for an Oscar for his 2004 film, Super Size Me, is responsible for a new fly-on-the-wall 3D documentary called One Direction: This Is Us, which follows the band for six months, including on their current world tour.

Billed as "more" than just a concert movie, it is supposed to give fans intimate access to the personal lives of Harry Styles, Liam Payne, Louis Tomlinson, Niall Horan and Zayn Malik, who have sold approximately 30 million records for Simon Cowell's Syco label.

Spurlock, however, describes himself as "a passionate music fan", who was also in the running to direct the documentaries recently released by Katy Perry and Justin Bieber. One Direction, he says, are an even greater prize.

"They are a phenomenon," he says.

"Right at this time now, their rocket is roaring through space. I'm just looking in through a window, and things have changed for them so quickly. In the last three years everything has transformed for them, and they're still just teenagers.

"So to have a snapshot of that moment is an unique opportunity for any director. And it's been incredible for me, never mind them."

One Direction were originally the runners up on ITV's X Factor talent show but quickly became its most successful - and lucrative - act ever, scoring number one albums in 35 countries.

According to Spurlock, his greatest challenge was to produce a real representation of the band's lives on and off tour - which was what they had asked for.

"I really wanted to do a film that didn't feel like a piece of pop - some kind of puff piece for One Direction. I really wanted to get into their lives and stories in a way that wouldn't feel like an advertorial for them."

With that in mind, he says it was One Direction themselves who selected him because of his body of work, which as well as Super Size Me, a critique of the fast food industry, includes 2008's Where In The World Is Osama Bin Laden and The Greatest Movie Ever Sold in 2011. It investigated product placement in film - although it cheekily funded itself by the same method.

Spurlock includes music journalists' views in the film - and they are not always kind

"I think they liked my sense of humour," says Spurlock. "And they genuinely wanted to offer fans something real about themselves. Also, I think I understand the way their circumstances have transformed. Before Super Size Me, my life was totally different. I was sleeping in a hammock in my office in New York,

"I was a $250,000 (£161,000) in debt and I hadn't paid my staff for months. I was a nobody. The film took off - and overnight I was thrust into the spotlight.

"And then there is the other side of the coin. I'm not a hater, as you guys say. When I made Super Size Me, people threw me under the bus really quickly and said 'oh, that guy's an idiot - his career will be over in a year'.

"The same is true of these boys, that some people just dismiss them as puppets. I'm somebody who likes to see other people succeed, no matter what arena they're in - and these guys are doing it. Better still, they understand the value of the gift they have been given."

Spurlock describes the film as "unscripted", and explains it gives fans unprecedented access into the band's personal lives - "intimate moments like Zayn giving his mother a house, or Harry returning to his first job, or Niall spending time with his brother just before his wedding".

But did the band's carefully protected image meant he compromised on both his "fly-on-the-wall" style, and editorial control? Spurlock says not.

"No, Simon [Cowell] and I are cool. He trusts me to do the job. And no, the band hasn't asked for anything to be taken out. Yes, of course there's a level of co-ordination, but we got to the point where they were comfortable having me in the room with them. We learned how to trust each other, by just spending a lot of time with each other off screen.

"They have their own private little world, because of the unique situation the five of them have found themselves in, so developing a rapport is crucial.

Harry Styles's mother has become a celebrity herself as a result of her son's fame

"Eventually they started to realise that I was investing in them, and they needed to invest in me and trust me. That grew over time. I needed them to be brave - you have to be to open yourself up to someone who is going to start chasing you round the world.

"It takes guts to open the door and let someone in, and eventually they decided to do that and that's why I can say honestly that it's not a show put on for the fans - what you see is real."

Can the film still be objective if their documentarian became so close to them? Spurlock says he includes the opinion of several music journalists in the film, who are not always kind.

"We ask them about the place of One Direction in music history, and many of them are negative. They say they don't deserve it, and success has just been handed to them. And those voices are important to my story, it develops a context for how different people are affected by them. And some of it isn't nice at all."

The director describes how he was "bewildered" by certain spectacles "the band now take for granted".

"For instance, the level of security they have to endure on tour. That was one factor we definitely had to take into consideration all the time, because every time they leave a concert venue they are chased down the street by hundreds of girls, and sometimes I was worried someone would get killed.

"Then there's their families, who have had to deal with so much intrusion over the last few years simply because they are close to One Direction. Harry Styles's mother has one-and-a-half million Twitter followers, how insane is that? You're talking about fans camped outside their houses. I couldn't quite believe what they've gone through, how they ended up in the spotlight because their sons and brothers are.

"The most astonishing thing I saw though was probably in Tokyo, which the guys visited for the first time in January. Japan was suffering its greatest snowfall for a decade and I saw dozens and dozens of little girls, camping out in the snow, holding placards and enduring those kinds of temperatures just to get a glimpse of the band.

"That's when I realised what I was getting myself into."

Having said that, Spurlock adds that the five "aren't bratty at all"

"They're incredibly grateful and very thankful for what they have. And they really recognise that it's the fans who've made them who they are, after being the runners up on X-Factor. They're beautiful guys. I think I learned a lot just by being with them."

One Direction: This Is Us is out in the UK on August 29th, 2013