Batman, the story of an ordinary citizen of Gotham City who adopts a disguise and heroic qualities to avenge crime, has undergone some weird and wonderful adaptations by Hollywood in recent decades. In 1989, the director Tim Burton captured some of the tale's gothic darkness; and in the last movie instalment, eight years ago, Joel Schumacher magnified its brassier, campier elements. In the intervening years, there have been several (unsuccessful) attempts to resurrect the series. But it wasn't until Christopher Nolan stepped in that the premise for the latest movie, Batman Begins, was forged: Batman needed to be grounded in reality; he'd be demystified; and other characters, such as Alfred (Michael Caine in the new film), would not be caricatures.

And so it began - the making of the prequel that virtually ignores all other films that came before it. Its focus: how Bruce Wayne learnt to be Batman. But how did the caped crusader's future - or, at least, his past - end up in the hands of a 34-year-old British director?

Everything about Christopher Nolan appears, on the surface, to be practical. The way that he dresses: charcoal suit and a blue Oxford shirt. The way he speaks: measured, unagitated, focused and direct. The way he sips tea and sits still. If you sat next to him on a plane you might think he was an accountant. Which is not to say he is boring. It's just his sober pragmatism betrays little about his sensibilities or achievements.

As somebody who has been compared to Stanley Kubrick - critics have also noted his eye for detail and his natural instinct for directing - after just three films, Nolan has the job of reviving the profitable Batman franchise, which is an immense risk considering the Batmobile has been running on empty for a while.

His rise to this position has been swift. After University College London, where he met his producer wife, Emma Thomas, he took a series of different freelance jobs directing corporate videos and industrial films. He shot his private project - a movie called Following, black and white, low budget - over 14 months of Saturdays. She produced, he directed; it went through the festivals, got worldwide distribution and attracted massive acclaim. The couple moved to Hollywood. His second film, Memento, an enigmatic thriller about memory loss that unfolds backwards, earned him an Oscar nomination for writing. And his third film, Insomnia, starred Al Pacino, Robin Williams and Hilary Swank.

We meet in temporary offices in Soho Square, while he takes a break from editing Batman Begins. It is a virtually all-British cast (Christian Bale as Batman, alongside Liam Neeson, Michael Caine, Gary Oldman, Tom Wilkinson, Cillian Murphy). And though locations included Iceland and Chicago (for Gotham City), it was shot primarily in the UK, at Shepperton Studios and in Bedfordshire, where the largest set in the world was built in a 300,000-square-foot converted zeppelin hangar.

One hour earlier, when Nolan was running late, I was introduced to Emma Thomas. We sat down at a table in her office, a sunny room crammed with Batman stuff - toys, figures, posters - from which she has to choose one image for the UK, one for the US. She and Nolan are equal captains of the ship: she handles the business and smoothes out the wrinkles so that he can focus on the creative elements.

Thomas told the story of how they met. Now, while working temporarily in London, they are living in the house Nolan grew up in with his mum, a former air stewardess who is American, and his dad, who worked in advertising and is British. Nolan has two brothers - one older who lives in Chicago; one younger, Jonathan, who wrote the short story on which Memento was based. We are on the subject of how to detect Nolan's Britishness, and how it plays out in his film-making, when Nolan walks in. He shakes hands and takes a seat at the table. Thomas stays on, clearly interested in his answer. I discover that the interview is with both of them and feel a sense of relief. With her there, he seems more at ease - within seconds it is clear he's not comfortable talking about himself.

"To me, Hollywood's always been international," he says. "Whether it's Hitchcock or Billy Wilder, Hollywood is an international language. When it's done in a specifically American way - for instance, with American comedies - they don't tend to play very well in the rest of the world. But as a language - when Hollywood cinema is at its best - it is universal."

There was not one specific thing, he says, that inspired him to make films; it was something he always did - making Super-8 movies throughout his childhood using Action Man figures. He would watch films from the 1970s: blockbusters like The Spy Who Loved Me, Star Wars, Raiders of the Lost Ark. Those movies made a huge impression - the escapist element in particular.

Born in 1970, Nolan grew up in Highgate, north London, before attending Haileybury boarding school, but not much more is known of what informed his young life. As film makers are storytellers, was there always a story he wanted to tell? "Not specifically. To me, writing has been a process of starting with reality and taking it to a more exaggerated place and examining it in an inflated way. Then it gets more entertaining."

He doesn't know what makes him choose a project: he just goes on instinct. It's certainly not calculated for a career move. With Insomnia, for instance, it was a compulsion.

"I saw the original Norwegian film and I was immediately struck with the idea of how you could do a remake, taking a very different view on things. I watched the film through twice in one sitting. And then I didn't watch it again."

His first film had a budget of £4,000; his third, Insomnia, $50m. More daunting than the money, perhaps, was finding the confidence to direct an actor such as Al Pacino.

"It is intimidating, but for me, it comes from having no choice. Someone said to me, 'Did Pacino take direction?' Well, yeah, he demands it. Because he knows how films are made and that's what's expected of you. I discuss everything as much as possible - all the problems with insecurity and communication. I include people in the process. I've found it's much easier to talk to everybody until they get bored of listening. Everyone knows everything you're doing and you just get on with it - no surprises, really."

There is a great deal of expectation that goes along with making a film in a series: the character already has a following, which can be a drawback as well as an advantage. What drew Nolan in, in spite of, and maybe because of, the preconceived associations, was the opportunity to work around them and the challenge to make a different kind of Batman film.

Even though the scope and the budget of this film are vast, for Nolan it still feels like a very personal movie. There is a recognisable reality this time, and he sees Batman as a regular guy. "An ordinary figure in an extraordinary world." Emphasising his ordinariness brings out what's most interesting about the character for him. Still, he knows he is making a great big movie. It has an emphasis on character and psychology but the feel of it is grand and epic in scale.

Batman was originally published by DC Comics. His plight - to avenge his parents' death - is brought on by the now-familiar image of Bruce Wayne's parents being gunned down, a string of pearls ripped from his mother's neck.

Later Nolan takes me into the editing room and shows me the opening 15 minutes of the movie. What works in his favour is that the film is completely different from those that have preceded it. "It's the story of Batman that should have been made in 1979 and wasn't," he says.

In the first 15 minutes of the film, the character of Batman in a bat suit never appears. Bruce Wayne (Bale) has been searching the world for ways to cope with his anger. There is the sequence of him in a Bhutan prison, where a monastic terrorist group, led by the Japanese actor Ken Watanabe, teaches him how to fight and instil fear through martial arts. Liam Neeson, playing Henri Ducard, Watanabe's right-hand man, also gives the lessons, and it is established that Bruce Wayne will use intimidation and the fear factor as his psychological weapons, when he eventually returns to Gotham and takes on the identity of Batman.

Unlike other comic-book heroes, Batman has no super-powers. He has the ability to inspire fear in his enemies, and in this film, Nolan worked long hours with his co-writer, David Goyer, and the production designers to create the perfect amalgamation of comic-book hero and independent character. The bat suit is new, less campy - more like a sinister wet suit with flexibility and movement, so now Batman can turn his head. It's been reported that the cape is made from fabric and becomes taut when hit with an electric current that passes through it - a sci-fi element taken from actual science.

Impressive too is the new Batmobile. Nolan wanted a combination of a Lamborghini and a Hummer, and the result is an original design that looks like a polished racer tank. In total, eight models were built, five functional, and it accelerates from 0 to 60 in just over five seconds.

Nolan's enthusiasm for filling a gap in movie history makes the choice of material more understandable. "It's a rare opportunity to find a massive story everybody is really familiar with but that's never been addressed. I think it's sort of an accident of chronology, in a way that when Tim Burton made his film there was such a demand to make the figure of Batman work and the idea of Gotham in a dark and gothic way - so that by its very nature it steps over the origins. There isn't one definitive telling."

But what drives Nolan is unclear. Not what drives him to make a specific film, but what it is, beneath the surface, that he is working out. Nolan admits that he can't imagine not doing this and can't come up with anything else he thinks he could do. "I don't mean to sound like I'm incapable of other things. I suppose if films didn't exist I'd want to be an architect - but I'd be pretty bloody miserable as an architect."

As a director, Nolan is not a shouter. And when asked what infuriates him, the silence goes on for so long that his wife begins laughing. When this happens, he offers an answer. "If you forewarn somebody about something and they ignore that, that makes me angry."

So how does he switch off? He doesn't. Occasionally he'll watch TV, but only when he's in America. "English TV - everything seems to be cooking programmes and fixing up houses."

When he's away from England, what he misses most is the "texture of the place". And now, living in his parents' place, staying with his wife in the bedroom he had from when he was three years old (they've put their kids in the master bedroom), that must be odd. An opening arises to delve into his childhood. What was it like? His response is swift. "Don't know, really."

"See," his wife says, giving him a gleeful look. "You've got your answers on Batman down pat."

When pressed, a shrug suggests that he's not intentionally guarded, it's more a reluctance to analyse something he doesn't consider a lot. He reveals that his childhood was fractured from moving back and forth from Britain to America, but he says when he went to boarding school it evened things out. With his parents still married, and no acknowledged turbulence or instability, there must have been something that shaped his unusual and dark sensibilities?

If there was, it's nothing he's aware of. "Chris is utterly straightforward," Thomas offers. "I think when my mother first saw Following - which had some disturbing undertones - she was shocked. She thought, 'Chris made that?'"

Nolan's films make you think of tormented, damaged souls. He wasn't one, so perhaps there was a specific experience that impacted him?

He shakes his head. "I don't think so. My life experience hasn't been extreme. In terms of specific things happening, no. I just draw from all the customary neurosis, really.

"I'm very surprised we're as successful as we are. I expected to always make films, but I didn't expect it to lead to success. It's quite strange to realise that that's where we've ended up. To earn a living, to be perceived as a person who does this job - but the truth is, we have two kids and another on the way, and it's far more bizarre to sit there at breakfast with the kids."

Their daughter, Flora, is 31/2 and their son, Rory, is 2. The most drastic shift in their lives has been becoming parents. "Nobody warns you," Nolan remarks. "It's all for the better, but at the time you're not sure. You wake up one day and suddenly you're in a position where you can't walk out of the house in the evening. Makes you feel like an adult."

When asked about being spontaneous he gets up to refill his cup and his wife teases him. "He has a spontaneous urge for a cup of tea," she giggles. "It's about as spontaneous as it gets."

Their affection for each other is evident and they are very much a team. When Nolan is pressed to offer what he believes is the perception of himself in Hollywood, Thomas has to refrain from answering for him.

"I'd like to think people think I'm honest and straightforward, but I have no idea if that's the case," he says. "Certainly, we're treated that way. They seem to value our honesty - we're down to earth and we tell people what we're thinking."

The business they're in has a high casualty rate: people burn out or become toxic, bitter and resentful. They couldn't seem more removed from this possibility, and while yes, it's because they ground each other, it's also part of Nolan's nature not to be part of the pack. He attributes this distance - his ability to stay removed - to being able to do exactly what he wants to do.

"Every film I make is my last film - that's how I view it. It doesn't mean I'm not intending to make another film. But I could get hit by a bus or something. I've never viewed it as a means to an end. We were joking on Batman Begins, 'Hey, if we pull this one off we'll get to make a big film!' But at a certain point you have to acknowledge that this is it - there aren't any bigger films."