IDOL has eaten America. To understand quite how gluttonously, you have to cross the Atlantic. You have to look at the newsstands, where, last week, three national magazines featured one or all of American Idol's star presenters . . .

Simon Cowell, Randy Jackson, Paula Abdul and Ryan Seacrest . . .on their front covers. You have to visit the supermarkets, where American Idol ice cream is flying off the shelves. You have to look in the record shops, where sales of American Idol artists have now passed 50 million units. And, of course, you have to turn on the television, where not only has American Idol's prime-time slot pulled as many as 41 million viewers, but where the show's enormous reach has launched the most unlikely of stars.

On last Tuesday night's live show, Ashley Ferl, a 13-year-old Idol superfan, was given the chance to meet her hero . . . a criminally untalented singer called Sanjaya Malakar, who had somehow found himself in the competition's top 12. Upon meeting Malakar, Ferl burst into tears, and became an overnight celebrity. On Wednesday morning, she was featured in national newspapers, interviewed on The Today Show, and signed autographs for her own fans. All this with the Idol finale still two months away.

Only in America, you might think, would this be possible. But no . . . only with American Idol is this possible. In its sixth series, while the internet and cable television have made huge inroads into US network television's viewing figures, Fox's American Idol has consistently bucked the trend.

America's record sales, too, have taken a plunge . . . but not those of American Idol contestants. To give just one staggering example, in the past two years, Carrie Underwood . . . the 2005 Idol winner and a singer largely unknown outside the US . . . has sold six million albums.

"What no one understands until they arrive here, " says Cat Deeley, the British presenter who moved to Los Angeles this year to front American Idol's UK programme . . ."is the scale of the operation.

When we premiered this season, the viewing figures touched 41 million. That's a ridiculous figure for someone from England to get their head around. For us, 10 million is massive. And, because they roll out the show across the time zones from the East Coast to the West, it almost feels like an advancing army."

The programme was created and produced by Simon Fuller, who managed the Spice Girls, and his company, 19, which brought Pop Idol to our screens in 2002.

And because 19 has first refusal on managing artists who win the competition, as well as the rights to publish the Idol compilations that have so far garnered almost three million sales, it is sitting on a gold mine.

Rough waters

Despite the strength of Idol's ratings (it has been a huge hit for TV3 which has broadcast it here from the start) and the enduring appeal of the recording artists it has discovered, 19 has occasionally encountered rough waters. Two years ago, Fuller sued Cowell, American Idol's biggest star, for ripping off the show with his own talent contest, The X Factor. Fuller and Cowell's dispute was eventually settled . . . Cowell kept The X Factor, signed a �20m-a-year deal to stay with American Idol until 2009, and kept a larger share of the show's earnings. Fuller kept his main man, signed a new deal with Fox, and took a share in The X Factor. The media made much of the spat, but Cowell was consistently phlegmatic. Indeed, he was quoted at the time telling Fuller to: "Lighten up. . . We can both get our shows made. Let's enjoy it." It's the sort of thing you can say when you're just about to sign a contract worth �100m sterling, and testament to the fact that both Cowell and Fuller have used Idol to become richer than Croesus. They are not the only Brits to have done so . . . the Idol headquarters, at the CBS Television lot in Hollywood, reverberates to the sound of bright English vowels.

Cowell, it seems, has no qualms about displaying his wealth. When the "talent" enter CBS by the back entrance, they are forced to walk past the chief judge's gleaming Rolls-Royce Phantom, which is parked outside the door of his personal "Star Waggons" trailer. Not that it seems to bother anyone . . .not only is everyone on the lot disarmingly chipper, their Persilwhite teeth seem to indicate they all use Cowell's dentist.

Beyond the Rolls, there is a car park where Bluetoothed apparatchiks ferry hassled producers around in golf buggies, and beyond that are the studios, where, on Tuesday morning, Cowell can be found in an Idol rehearsal room with his fellow judge, Randy Jackson. Once a bassist with Journey and Billy Joel, Jackson is an engaging character, and this morning he and Cowell are bantering like old mates. Presenting the show has, apparently, become so old hat that Cowell was half an hour into last week's Tuesday afternoon feed to the nation when he turned to Jackson and asked: "Are we live?" It must be terribly boring earning all that money, I say. When is Cowell going to jack it in?

"Well we've been doing this for a while now, " he says, his expensive smile lighting up. "And every year on the show is like a dog year . . . it feels like seven. I've got three more seasons under contract, and then, I think, that's enough. . . I remember when we came out here in the first year we had a great time. It was an adventure then. We genuinely didn't know whether the show was going to be a hit. Sometimes the getting there is more fun than the being there."

But he must find some gratification in seeing his proteges take the world by storm?

"Sometimes, if we like them, " he says. "We liked Fantasia [who won Series Three]." What about Jennifer Hudson, the singer who came seventh in the year Fantasia won?

She won the Best Supporting Actress Oscar for Dreamgirls, yet failed to mention Idol in her acceptance speech.

"I was expecting that, " says Cowell. "The one thing that got me a bit ticked off was when she gave an interview afterwards and words like 'abuse' were mentioned in our treatment of her. We gave her incredible feedback on the show, and Randy actually put her back in the show twice, when the public had voted her out. It wasn't as if we were expecting flowers, but she might have said 'thank you'."

Hudson will not be making a guest appearance on Idol any time soon, but, in the past two seasons, a host of big names have . . . including such distinguished musicians as Mary J Blige, Gwen Stefani and Prince. Has this lent the show some much-needed musical credibility?

"Oh, I don't think it's got anything to do with credibility, " says Cowell. "It's got something to do with 25 million viewers. Trust me, with those numbers, we could be a cooking programme with a music slot and we'd get the same calibre of people." Anyway, says Cowell, they're not always such big stars.

This week's musical theme is, appropriately enough, the Sixties' "British Invasion", and joining Lulu as a guest star is Peter Noone, once of Herman's Hermits.

"I don't think the stars were begging us this week, somehow, " he giggles. "Yeah, we've been offered Beyonce, Paul McCartney and J Lo, and we call asking: 'But are Herman's Hermits available?'" With that, Cowell is off to his trailer to smoke a cigarette or five and watch the television feed of the dress rehearsal. This is, he reveals, where he and Jackson give themselves an idea of what comments they will make when the show goes live. Cowell seems underwhelmed by the prospect.

Doesn't he think he has found a star this season? "I think we have a couple of good singers, " he says, with unusual tact. "It's not until you put them on the same stage as Beyonce that you know you've got a star."

The live show, where 11 contestants perform one song to keep them in the competition, rather proves his point. There is a palpable lack of star quality on display . . .

a fact that does not escape Cowell's attention. "I thought it was flat, " he moans to one. "I think you've lost your edge, " he says to another. "You sang it beautifully, but God it was depressing, " he says to the next. But while the action on stage may not be enthralling, the audience provides ample entertainment.

In the front row, sitting next to minor celebrities like the actress Melissa Pile, is Ferl, the lachrymose teenager. Behind them is Nigel Lythgoe, who was known in his presenting stint on ITV's Popstars as "Nasty Nigel", and who is an executive producer on Idol with Ken Warwick, another Englishman. In the regular and lengthy advertising breaks, Lythgoe chats to presenter Ryan Seacrest and the judges. Is he putting words into their mouths?

"No, but I am making suggestions, " he says. Simon, he adds, is being "very naughty . . . he's winding Paula up, saying how good he thinks Lulu is, and how they might replace Paula with Lulu as a judge.

And, I'm winding her up even more by telling Ryan, so that he can be in on the joke, and say how great Lulu is as well." If Cowell's aim is to aggravate Abdul, it seems to work. In the ad breaks towards the end of the show, she starts to rain down ever less playful punches on his torso.

Further back in the audience sit previous contestants, including a leggy brunette called Antonella Barbra who gained some notoriety last month when a selection of immodest pictures of her were published on the internet.

Slick and homespun

The production veers between being regimentally slick and worryingly homespun. Cues and lines are delivered on time, from the right places, but microphones splutter, placards obscure autocues, and the judges do not take their seats until seconds before the show goes live. It's easy to see how Cowell was confused last week . . . the whole thing feels like a dress rehearsal, albeit one in which the audience are violently involved.

On Wednesday morning, the day after the live show, the Idol production offices are buzzing. This is a big day for the production team, who are not only smoothing over the fine details for tonight's results show, but also beginning to think about next week's engagements.

There are CDs containing possibilities for next week's song choices to compile, celebrity guests to keep happy, and new format ideas to discuss.

Ken Warwick is in his office, tinkering with a new set design for the Idol stage. He's been with Idol since the start . . . so what does he think is the secret of its success?

"There's no secret, " he says. "In America, everyone wants to be famous. That's what it's all about.

That's the golden fleece. They all want to walk into a restaurant and be recognised. It's a religion here . . .
not a very healthy one . . . but there nonetheless. The prize we offer isn't a record deal, it's stardom.

That's the whole ethos of the show.

You can be flipping burgers one minute and then, three months later, you are a huge star in America. We offer a fast track, short route to stardom, and that is very, very appealing to many people."

It may be hard to believe now, but when Warwick, Lythgoe and Fuller first came to America in 2002 (with Pop Idol under their belts) to find a network for American Idol, they came up against a brick wall. In the end it took Rupert Murdoch's Fox network to put the show on, and only after some serious wrangling.

Six years later, Idol is stronger than ever, and rival networks are ruing the day they let Fuller through their fingers. When Jeff Zucker, NBC Universal's President and CEO, says, in a sentence that could only come out of a television executive's mouth, that the show "is the most impactful show in television history", he must do so through gritted teeth.

If you are looking for its unique appeal, says Warwick, you should look no further than the very reason other networks rejected the show in the first place . . . the sarcasm of its star judge, and the cruel streak that runs through every stage of Idol.

Does he ever think the show is too cruel in those early rounds?

"Do I think we shouldn't put those people on television?" he asks. "I don't know. Are they entertaining?

Are they funny? It's my job to show the talent of any place we visit, and that involves showing some very bad people. We might as well show the funny bad ones."

The formula clearly works. But now he's proved himself, and made a mint in the process, isn't it time to move on? "Sometimes, because we're such a successful show, the politics can get a little tiring, " he admits. "There are battles that go on between different departments, and arguments with people whose job it is to get as much of their product on screen as possible. I know the revenue we get from our sponsors [like Coke and Ford] is massive, but our job is to protect the show. We need to be able to integrate their presence naturally. . . If you let the wolves in, they'll tear everything to pieces."

Wednesday night's results show is half an hour . . . or 22 minutes in commercial television time . . . comprising mawkish drama and the limited musical talents of Peter Noone. A friendly-looking girl called Stephanie is evicted, and then asked to sing through floods of tears. It's over for her, but the Idol army marches on.

On the way out of the studio, one again has to pass Cowell's Phantom. This time, there is a man in a hat holding the door open, while, in his trailer, Cowell is sitting barechested as a barber trims his sideburns. He's lost in thought. Is he thinking about Stephanie? Probably not. More likely, he's considering what to do with the rest of his week, now that his contracted two hours of American Idol work . . . for which he was paid �384,616 . . . are up.

American Idol is shown here on TV3