In April last year, one American port welcomed more new immigrants in one week than any other place in the history of mankind. Its name?

Liberty City.

Liberty City makes Batman's Gotham look like a funfair ride. Here, the American dream has curdled, soured and grown mould - drug-dealing and car theft are not only rife, they're endemic, and if you want to get along, you have to play the game.

Fortunately, this metropolis exists only in the imagination of the people who created Grand Theft Auto IV. On its first day on sale, the game sold 3.6 million copies worldwide, generating around $300 million in income. By comparison, Batman: The Dark Knight, managed $70 million on its opening day.

Now Liberty City has returned to star in the latest adventure in the Grand Theft Auto series: Chinatown Wars, an all-action game for Nintendo's best-selling DS handheld console.

But where does this nightmare vision of America gone wrong spring from? New York? Detroit? Los Angeles? Nope. Try Yorkshire.

Five minutes by cab from the centre of Leeds, on the first floor of an anonymous boil of an industrial estate, is the home of Rockstar Leeds, the northern English outpost of the company that in its 11-year existence has generated more controversy with its games than any other. Manhunt (sequel banned in the UK), Bully (release delayed and name changed to Canis Canem Edit), Midnight Club (illegal street racing), and of course Grand Theft Auto. They're all Rockstar.

The Leeds division of Rockstar specialises in producing handheld games, and Chinatown Wars is its first game for the DS, a console more commonly associated with brain training or rearing virtual ponies than drug dealing and car theft. More controversy seems guaranteed.

Never before has the company opened its doors to an outsider. I am allowed to look around, as its 80 employees sit in open-plan silence at blinking screens, tweaking, playing and testing Chinatown Wars and other games whose very existence the company will officially deny.

Such is the air of secrecy that all photography is banned. Not one of these people is free to talk about their work with anyone outside the company. The atmosphere is intense with concentration, but of the sort that comes when people are love with their work rather than enslaved by it.

At the head of this secret society is Gordon Hall, a veteran games designer who leads and inspires his team with a combination of perfectionism and approachable bonhomie. He tells me how it all comes together.

“I have my own office, but when we are making a game, I come and sit here, right in the middle of the floor, with my lead designer, lead programmer and art director an arm's length away. If I sit here and talk, then everything ripples out across the office, so that everyone is clear about what we are doing.”

The company is run along clear rules. “Rule one,” says Hall, “is that every other meeting takes place down the pub, where we can talk and the ideas flow. See that road over there? There's a pub up the hill that'd go out of business if it wasn't for us.”

The key to making a successful game is rule two. “We may only have 16 people working on a title at any one time, but as far as I'm concerned, all 80 people here are games makers. Once a week, we have a day where we stop work, and everybody in the office, my PA included, will play a portion of the game we're working on at random. We listen to everybody's comments and try to make improvements accordingly. Over the two years we've been working on Chinatown Wars, everyone you see in here has played every single section of the game. We all know it inside out.”

And what of the controversy that the game is seemingly sure to attract?

“Look. The games industry is still in its infancy. We've not begun to touch on what it can be. I think we've won the battle to call ourselves entertainment, but games still carry this image of being cartoon-like and for children. This is absurd when you consider that the people who founded this industry are now 25 years older.

“I want to get to the stage where we can produce a game for adults without people being shocked by the fact that we've done so. The DS is just a piece of hardware. But what is there for young men on it? Nothing.”

As I leave the office, I notice that beneath the Rockstar office is the northern headquarters of a company that collects and administers road traffic fines on behalf of the government. Its employees sit in rows, pecking at their PC keyboards like battery hens. How many of them, I wonder, will escape for an illegal drive in Liberty City this weekend?

GTA: Chinatown Wars is out on the Nintendo DS.

Explore Tech & Web

• Personal Tech

• The Web

• Gadgets & Gaming