Here's a story. It's an Eddie Izzard story, about Eddie Izzard, so it veers round the houses and back and forth. He's packed a lot into his 45 years; yes, even into the two-thirds of his life that happened before he got famous. Stick with it. Like many an Izzard story recounted from the stages of comedy clubs, theatres and arenas around the world, it's worth it. If you imagine it recounted in his slurry speaking style, it's even better.

ddie Izzard has hitchhiked from Sheffield to Birmingham. He's been living in the student area of the Steel City, sleeping on mates' floors, despite having abandoned his degree (accounting, financial management, maths) after only one year. He'd never really wanted to take a place at Sheffield University anyway, or study bean-counting. His big plan had been to go to Cambridge, 'do the Footlights, then go to Edinburgh [Festival] and then boom, you get a career - they give it to you on a plate'.

But at boarding school Izzard had decided to give up on his A-levels. 'I thought I wasn't cool enough. So I thought: I'll stop studying! That'll make me cool! It's like cigarettes. Why are you smoking? Because they're cool. And then maybe I will get to talk to girls.'

The result of his poor results? Cambridge was out, but Sheffield would have him. Izzard took a proper degree course to please his dad, a financial officer with BP.

But, after one year, he's ballsed that up as well. And now Izzard is that sad figure: the drop-out who hangs about the university union. He's putting on student productions with his own group, the Official Touring Company of Alpha Centauri. He's trying to persuade his contemporaries in Sheffield University Fringe theatre company - among them Stephen Daldry, future director of Billy Elliot - to take shows up to Edinburgh. But Sheffield's undergraduate thesps don't share his enthusiasm. They lost money the last time they took a show to the Festival. Sorry, Eddie.

So Izzard resolves to make his own luck. Hence him thumbing a lift to Birmingham. It is the early Eighties.

'I got dropped off at Spaghetti Junction, right in the middle of one of the humps,' he recalls. Izzard caught a bus into the city centre, to find a payphone. 'They'd just changed from the pips to the thing where you put all the money in first. People wouldn't know you were in a phone box. You could be in an office.'

Izzard's big plan, based on a scam that Peter Sellers once pulled, was calling the local television studios where they made OTT, Chris Tarrant's late-night, grown-up version of his kids' show Tiswas. 'I was a big Tiswas fan. And Alexei Sayle had been on OTT.' Izzard thought he could get on the show, too.

His idea was to ask for Tarrant's agent, so he could hear what his voice sounded like. Then he'd hang up, call back, ask for Tarrant and, impersonating Tarrant's own agent, recommend a hot talent named Eddie Izzard for OTT. In fact, Izzard was in reception right now... maybe Tarrant could pop down and see him...

Did this plan work?

'Nnnnoooo,' says Izzard, rolling the word round his mouth. 'No. Because the agent was in London all day. About 5.30pm I was phoning up the office pretending to be him - his name was Harold - never having heard him. "Hello Shirley, it's Harold." "Oh, hello Harold."' Pause. '"Which Harold is this?" "Oh fuck."' And Izzard mimes hanging up, abruptly, in frustration.

And then, after a long day's nothing, Izzard hitchhikes back to Sheffield. 'Those are the things I used to do,' he sighs. 'My dad said this thing recently: "You always had stupid ideas - but now some of them have worked." That's the difference. And I did - when I was 14 I decided to cycle from Sussex, where I was living, to Wales, where we used to live, with no money, in order to lose weight, because I kept eating chocolate.'

And did he?

'I did. My dad gave me a bit of money and a Little Chef map, so I just cycled from Little Chef to Little Chef. Four or five days camping in farmers' fields.'

You were single-minded/mental.

'Yessss ... mental,' he says absent-mindedly. 'I have big crazy plans. AND!' Izzard's bendy and expressive voice, as it is wont to do, suddenly stands straight up to attention, in capital letters, before sliding into italics. 'I've still got some of them!'

I have travelled by taxi many miles north of Sunset Strip, Los Angeles, to a place called Santa Clarita. It's not very nice. A low-level industrial estate flung either side of a raging torrent of a freeway. 'Santa Concreta I call it,' says Eddie Izzard when I meet him inside Studio 10 at Santa Clarita Studios.

For someone ubiquitous in the British comedy ether for much of the Nineties and early Noughties, we haven't seen much of Izzard recently. And this is why. He's been holed up in LA, most recently in this vaguely dispiriting backwater, working on the next phase in his plan for world domination: a lead role in an American TV drama series called The Riches

He had his first meeting about the show in November 2004. The TV people hired him straightaway. He thinks his performance in Peter Bogdanovich's film The Cat's Meow, and 'getting the Tony nomination and all those other awards' for his 2003 Broadway appearance in A Day in the Death of Joe Egg, put him 'in a decent place' with the TV executives. In early 2006, they shot the pilot. Late last summer The Riches was greenlit. It's a big deal. Enough to make Izzard forgo what sounds like a plum gig in the latest series of 24 - he would have played an unscrupulous arms dealer, one of whose nuclear weapons goes off 'in the wrong place'.

Today, on a set kitted out like a spacious kitchen, they're filming show five of the 13-episode series. Within seconds of us saying hello between takes, Izzard is telling me how he's been based on the West Coast on and off for three years because 'tactically and practically' it gives him a better vantage point from which to 'flood out' into the US entertainment business. He remembers, years ago, making an American TV show in the UK - an episode of Tales From the Crypt with Ciaran Hinds - and how the actors were paid 'scale'. That is, minimum fees. The Americans were members of the Screen Actors Guild (SAG), while the Brits belonged to Equity. SAG's scale was much better than Equity's scale. That's another reason to be working in the US, and to be a member of SAG. So long thwarted - first by being a slack-arse at school, later by the miserly crowds who didn't take to his surrealist act during his years as a street-performer - Izzard will not now be denied.

'My first year [performing] in Edinburgh I saw Stephen Fry, Hugh Laurie and Emma Thompson win the Perrier Award [for Best Comedy act]. That was '81. My last year in Edinburgh was '93. That,' Izzard says with a slight shrug, 'was my 12 years of climbing the mountain.'

Today, he's looking slim, trim and manicured. The blow-dried, blond hair. The sharp goatee. The midnight-blue power suit. It all speaks of a successful professional, and of someone who's doing very well for themselves, ta very much, in Hollywood. Finally. He will say that, 'I always wanted to do drama and films,' and that he only moved into comedy because, as a spotty teenager with greasy hair, he felt he couldn't play a romantic lead. He certainly wasn't pulling any girls. But he could make people laugh. He pursued that instead. So comedy was a 20-year detour on the way to an acting career? 'It kinda was,' he says with a frown and a grin.

He happily admits that, having started late, he's been playing catch-up ever since. With Robbie Coltrane, Jim Carrey, Robin Williams - with anyone who has managed to defy their comedy roots and be taken seriously as an actor. With Hugh Laurie, who, a couple of weeks before our meeting, won his second Golden Globe award for his role in hit US medical drama House. 'And I'm pleased that Hugh is doing...' He tails off, as he often does, but I presume he was going to say 'well'. 'Because I'm trying to do exactly what Hugh is doing.'

The Riches is being made by the American channel FX. It's 'a Channel 4-y thing', explains Izzard, albeit one that's carried in 90m US homes. He's acting alongside fellow expat Minnie Driver. They play husband and wife Wayne and Dahlia Malloy, grifter members of a gypsy travellers community. After one scam too far, Wayne and Dahlia decide to take their three children and 'go legit', by adopting the identities of suburbanites, Doug and Cherien Rich.

But Dahlia is not long out of prison and wrestling with a crystal meth habit. And Wayne has to assume the life of Doug Rich, a high-powered lawyer. They're dispatching their chavvy-cum-savvy children to the poshest school in the neighbourhood. The midnight-blue power suit, then, is Rich's, not Izzard's. But it fits the Brit multi-tasker just fine. Izzard is also an executive producer on The Riches, and is helping with the writing. But there are eight other producers, and a network keen to make this high-profile drama work in the competitive American TV market. How does Izzard, an avowed control freak, cope with jumping to others' tunes?

'Completely fine, because I didn't write the whole thing,' he says. 'I've been studying structure in order to write dramatic stories, as opposed to my stand-up, which is very free-form.' He's been spending time in the show's 'writers' room, learning at the table... And I seem to be quite good at pitching ideas in.'

His 45th birthday was earlier this month, but he looks younger. With the help of a personal trainer and what sounds like a scary kind of dieting, he appears far healthier than he did in his lumpy, floppy thirties, after success at last came knocking. 'When you start earning money you can eat, snort or drink your wages. I started buying food and I got a bit too heavy. I didn't know how to control it. Then I started pulling back and back and back... and now I don't need hardly anything. I thought, they've given me this lead role and I should try and be as lean as I can.'

I watch Izzard and Driver film a scene in their new kitchen. Driver is dressed in a mini-skirt and knee-high boots. Izzard, famously the only transvestite in the mass-media village, admits to enviously eyeing up Driver's four-inch heels. Both Driver and Izzard say their lines in convincing American accents. He's been working hard on his, and on his acting - his coach is on set and on hand at all times, helping him improve his craft.

'FX said to me, "Can you put a little bit more light into the darkness?"' Izzard says of his contributions to the script. 'So more of my comedy has been allowed to come into it. But with a complete bracket round it that I've worked out with my acting coach. I said, "Let's analyse it, let's distil what the hell I can take over from comedy." And it is: whatever pertains to Wayne's universe that I can use. But it cannot have cats and dogs talking to each other. It cannot have James Masons and surreal people.'

He gives me a tour of the set. I ask Izzard if we must give The Riches, like Desperate Housewives, the voguish classification of 'dramedy'? He almost winces at the term. 'I prefer to call it drama with a funny underbelly. I've been trying to get out of comedy for so long, I don't want to get stuck halfway.'

As we sit down in his trailer parked out the back of the studios to talk properly, I wonder: how did Eddie Izzard - rambling comic raconteur with a thing about James Mason and conversations between pets - get here, from the British comedy circuit to Hollywood? By applying the same single-minded focus that took him and his 'A-level bullshit skills' from Sheffield to Birmingham, and him and his bike from Sussex to Wales. By shaping his career like he's shaping his body. By being utterly, utterly dedicated to getting on and getting ahead.

Over the past decade he's conquered stand-up comedy with a series of acclaimed one-man shows, international tours, including gigs delivered in French. He talks about 'taking New York' and 'getting Paris' and about how, once he gets back to stand-up, Germany, Russia and Spain - and jokes in their native languages - are next on his hit list.

'I was just smashing and grinding these shows out,' is the way he describes his early days gigging. It's odd language for someone who, on stage, comes over as a big softy who says 'cool' and 'groovy' a lot. But this funny stuff was a serious business, and in business you need to be aggressive. 'I played all over, kept going everywhere, until I could pay for the cameras to film one of my shows.'

He became a member of the Association of Independent Producers when he was unemployed in his twenties, and learned the lucrative importance of retaining his copyright on his filmed performances. All his top-selling videos and DVDs, made by his production company Ella (named after his mother, who died of cancer when he was six), repaid his investment many times over. 'I think I earned my accountancy degree.' His last stand-up show, 2003's Sexie, played to sell-out crowds across the world for five months.

But he'd also had an acting agent since 1993, the year of his breakthrough comedy show in London, at the Ambassadors theatre. Parts in movies - not lead roles, but nor were they bit parts - have come his way: The Cat's Meow, The Avengers, Velvet Goldmine, Ocean's Twelve and, this summer, Ocean's Thirteen. He was most recently on the big screen in My Super Ex-Girlfriend. He played an evil criminal mastermind out to nobble Uma Thurman, the vengeful - and super-powered - ex-girlfriend of Luke Wilson. Coincidentally, I saw it on a plane on the way back from my LA meeting with Izzard. It's harmless enough (I laughed a few times; jetlag, I think), a C-list comedy starring an A-list comedian. When we speak later, on the phone, I ask him why he took the role.

'I know how to do comedy in stand-up gigs. But comedy in a silent format, where you haven't got an audience's laughter to work from, is harder to do. You have to learn to judge it.' With filming on The Riches coming up, it seems he thought that even for a show with only a 'funny underbelly', the practice would be handy.

But before The Riches hits our screens - it premieres in the US next month - Izzard can be seen flexing his acting chops in a British TV drama. Channel 5's Kitchen isn't quite the weighty role that he craves. But, being a hefty two-parter running to four hours, it's a pretty good start. And it's better than 40, the 2003 Channel 4 production in which he was miscast as a testosterone-fuelled advertising executive.

Izzard plays Nick Malone, an alcoholic chef in a top Glasgow restaurant. His staff is a rum mix of cheeky young scammers and boiling-mad older hands. One protege gets caught up with the glamorous wife of a brutish patron, who's also his probation officer. Malone is engaged in a messy divorce and a war of words with a food critic. Imagine Anthony Bourdain's Kitchen Confidential peopled by some Gordon Ramsay and Jamie Oliver clones. It's not the most inventive of scenarios in these days of foodie overload, but Kitchen is energetic and full of narrative brio. And Izzard is great.

Before nipping over from America to Ireland for the shoot (it's cheaper to shoot in Dublin than Glasgow), he brushed up on his kitchen skills in a Los Angeles eatery, Grill on the Alley. He used to cook a lot when he was younger, 'until something happened and I stopped'.

What happened?

'A family fight - something emotional. I can't actually talk about it.'

I admit that I can't tell if he's being serious.

'I am being serious. I used to cook with my mother. After she died I kept cooking. And at boarding school I was in cooking club. Then at 13 something went wrong and in a childish way I spun it into, "I'm not gonna cook any more." And I haven't till now.'

He's proud of Kitchen, even if he didn't have sufficient time beforehand to prepare a Glasgow accent, and even if, really, 'the co-leads are the younger ones. My role is smaller. But it's one of those roles like Judi Dench in Shakespeare in Love - they're on screen less but are talked about all the time and have a lot of presence.' Dench, you may remember, won an Oscar for the eight-minute performance to which Izzard is comparing his role in Kitchen

If he was a pop star or a 'straight' actor, we'd call Izzard a careerist, or a name-dropper, or an egomaniac. Here he is, for example, talking about his reappearance as 'technicians' technician' Roman Nagel in Steven Soderbergh's upcoming Ocean's Thirteen: 'It's interesting filming with George and Brad because the camera stays on them - I mean, they're good-looking guys. But the camera's waving around following them and you've got to try and get your face in.'

So why do we forgive Izzard his craven ambition? Because he's honest and direct: about his goals, his weaknesses, his drive. He only wants to entertain, and he only wants to get better. 'I think my ambition was always there, and it was held back for a long time because nothing ever happened. And if you think you can do something and it doesn't happen, and everyone tells you it won't happen, you have to hold on to what I call the Madness. I will just hang on and keep going and keep going until ... the thing gives in.'

We forgive him because he's still openly bereft at losing his mother at such a young age, and ascribes his lust to entertain to that loss. 'I've analysed it,' he admitted in an interview with his friend Bono last year (they both supplied voices for the upcoming animated film Across the Universe). 'I think the desire to perform has something to do with my mum dying, because I don't remember wanting to perform before that. She died when I was six, and at seven I saw a kid on stage in a play and I thought, I want to do that, and that feeling stayed.'

We forgive him because he's clever and ethically engaged: he doesn't just want to tell jokes in French, Russian and German to show off (although that is part of it). He's a passionate believer in the European Union, in the notion of the ethnic melting pot as a force for good. He even accompanied Tony Blair to Brussels last summer to report on a European Council meeting; you can still find his podcast on the Number 10 website.

Because he's intriguing, a purist who, for all his ubiquity, remains a bit of a mystery. I suspect he may have a girlfriend right now but he has always, always managed to keep his relationships private. I ask him if he's in a relationship, and he replies: 'I always keep that kind of closed. Certain people in my family and certain people I have relationships with don't wish to be judged through my whatever ... So I tend not to talk about it.' He wears dresses and make-up, but even after the acres of newsprint discussing his transvestism, it's still strangely unfathomable; and I mean that in a good way.

And because, frankly, he's a genius; if you've got any gift tokens left from Christmas, buy the Eddie Izzard MMVI box-set DVD - 573 minutes of six live performances that'll have you laughing until Easter.

And we forgive and indulge Eddie Izzard because, unlike plenty of other fat-cat celeb entertainers, he refuses to rest on his laurels. With his acting, he's still getting there, as I'm sure he'd be the first to admit - although in Kitchen he gives a brilliant performance, all gimlet-eyed intensity and hungover tripwire temperament. Just like a real chef, you think. It's not funny in the slightest.

Back on The Riches set, we talk in his trailer and have dinner in the canteen. Chicken and green veg for Izzard. While we are eating, one of the show's producers reads out a review of the pilot episode, by the TV critic of the Denver Post. It is their first review, and it is a corker. Izzard's performance is described as 'phenomenal', Driver's 'wonderful', and the show as one of the most 'promising new heavyweights' on TV.

'We don't always do this,' Izzard whispers out of the side of his mouth as cast and crew all clap and cheer and holler like Americans. 'Actually, we've just put it on for your benefit.'

Then he leaps out of his seat and bounds into the middle of the canteen floor. He thanks everyone for their hard work, gees them on for the rest of the four-month shoot, and promises that he'll know everyone's name very soon.

'So obsessive,' mutters Driver good-naturedly.

Of course he is. Izzard isn't going to take any risks with The Riches. He remembers the missed chances, the unappreciated routines in Covent Garden, the bad days in Birmingham, as if they were yesterday.

'If you get too established in comedy, people get addicted to the druggy nature of comedy,' he thinks. 'You're releasing endorphins ... No, you're releasing ser-o-to-nin,' he says, savouring every syllable, 'in the brain. And people become serotonin junkies because it's great. You just get these hits [he clicks his fingers three times] and it is like coke, bam bam bam. And I feel that drama is like carbohydrates with minerals, vitamins. It's a main meal of a thing. With lots of different tastes and variances. And it works in a different way on the palate.

'After my big scenes in Ocean's Twelve and Thirteen, it feels like I've got to the Himalayas. I'm at base camp. It's slightly frustrating at the same time. I'm here, I've had a couple of scenes - now can someone just give me a big frigging slice of a film role and I'll tear through it! But I've got to keep hacking my way up the mountain.'

· Kitchen is on Channel 5 at 9pm on Wednesday 28 February and Thursday 1 March