Meet Steve Coogan: Action hero. (Is he having a laugh?)

The great clock at Lime Street station shows midday as my train rolls into Liverpool. It is, in fact, 10 minutes to 11. Within quarter of an hour, I am standing with a small crowd in Castle Street, near the splendid City Hall, watching Steve Coogan slide on a wire from the roof of one high building, across the street, and on to another. My sense of disorientation is enhanced by being ushered by the PR man through the half-constructed set of a large bank (complete with chandelier, Steve Coogan for the swinging on), up several flights of stairs, and onto a rooftop walkway. From here I look across to where the comedian - standing on scaffolding surrounded by gaffers, best boys and grips - is about to begin his descent. It's too windy and high for me, so I retreat back down again. What some are prepared to do for comedy, I am not prepared to do for journalism. And perhaps Coogan is just brave, or perhaps he has forgotten that he's in Liverpool.

The great clock at Lime Street station shows midday as my train rolls into Liverpool. It is, in fact, 10 minutes to 11. Within quarter of an hour, I am standing with a small crowd in Castle Street, near the splendid City Hall, watching Steve Coogan slide on a wire from the roof of one high building, across the street, and on to another. My sense of disorientation is enhanced by being ushered by the PR man through the half-constructed set of a large bank (complete with chandelier, Steve Coogan for the swinging on), up several flights of stairs, and onto a rooftop walkway. From here I look across to where the comedian - standing on scaffolding surrounded by gaffers, best boys and grips - is about to begin his descent. It's too windy and high for me, so I retreat back down again. What some are prepared to do for comedy, I am not prepared to do for journalism. And perhaps Coogan is just brave, or perhaps he has forgotten that he's in Liverpool.

Coogan is making his first movie as a star. He has co-written The Parole Officer (a provisional title), which is being made in association with Universal Studios. True to the traditions of Britcom, it features a hapless nebbish (in this case a probation worker) who has to overcome the consequences of his own naivety with the assistance of an ensemble of ne'er-do- wells. The probation officer (Coogan himself) - framed for a murder - has to prove his innocence by breaking into a bank, and he enlists some of his former clients to help him get in. Among his helpers are Om Puri, who starred in East is East, and Stephen Dillane. The film will be out early next year.

I meet him in a large, bare room in the building below his scaffolding. At the other end, the production team eat croissants and swap jokes. Coogan (still in his boilersuit and safety harness) and I occupy the only two chairs. He sits by the open window so that he can smoke without bothering me. Not many celebs are that considerate.

I know he's supposed to be a bit flash, with his fast cars, faster love life and fashionable bar-hopping (after all, this is the man the Sunday Mirror once described as a "millionaire who owns flashy cars and has a stream of glamorous women battling to appear on his arm"), but if I was expecting Peter Stringfellow with a human being's haircut, I was dead wrong. For a start Coogan is so bloody young. He could be 22. His face is fresh and ruddy, and he's wearing steel-rimmed specs. Instead of the smacked arse of Alan Partridge's face, Coogan's expression is serious and thoughtful, and he doesn't wait for me to ask the usual questions, but launches straight into a discussion about television, its role in the national conversation, and where comedy fits in. Like there's a log jam that needs to be broken. "I haven't talked about my work for a long time," he tells me.

But then, we've hardly seen anything of him. Knowing me, Knowing You was made way back in '94, when Michael Howard was Home Secretary. It took another three years for the dreadful sports commentator, Alan Partridge, to reappear in the famous series in which he was on the skids. Since then Coogan has not really been on telly at all. He spent most of a year on the road in his acclaimed one-man show, but apart from that, he's nearly a stranger. If he'd been Stephen Fry or Ben Elton, he'd have got through two novels, a musical, a play in New York, an opera in Milan, a short book of verse, and spent every Saturday playing the sax at Ronnie Scott's till four in the morning. So what's with the reticence?

"I'm not very quick," he says, deadpan. "I'm slow. It took me and the team nine months to write six half-hours of I'm Alan Partridge. But if you build a reputation, it's better to take the time and get it right. I was also very reluctant to do another half-hour sitcom because it would be compared with Alan Partridge. And I wasn't prepared to do just anything. My agent would say to me, 'your stock value will plummet if you do this or that', so I didn't."

If it took them so long to write Partridge, I ask, why didn't they assemble a team so that, like Seinfeld in America, there could be 30 episodes of Partridge a year, rather than six every four years? "I'd love to do a Seinfeld," says Coogan, "but there's not enough money here to hire good enough writers. And it's a bigger country and they have more writers to choose from."

But Coogan and I both know that's not the only reason. When he talks about Alan Partridge, he is talking about his own personal daemon, not some commodity. So deeply did he and his colleagues (Armando Ianucci and Peter Baynham) care about Partridge that they constructed a vast, unseen hinterland for him, to explain why he might behave in this or that way. They'd never, I think, have given Partridge up to other writers.

Not that he didn't get on their nerves. "You can imagine," says Coogan, "spending all day cooped up with him. Armando used to say: 'Shut up, stop talking, you horrible man. What a nightmare you are!'" The rest of the team would sometimes try and take revenge on Partridge through the plot. Occasionally, Coogan was forced to defend his alter ego: "There were times, when they'd do something with him and I'd say, 'Leave him alone, there are bigger bastards around'."

But not many. Partridge was a monster. The egotistical, cowardly midi-celebrity with Daily Mail values, became the terrified, career-blighted early-morning local DJ desperate to sell dumbed-downest ideas to BBC executives. Ideas such as Swallow, a regional detective series based in Norwich; Knowing M.E. Knowing You; Youth Hostelling with Chris Eubank; Yachting Disasters. And Ladyshapes with Alan Partridge. The writing captured the relentless search for mediocre novelty that characterises much modern media.

In fact, if anything, Partridge strove too hard to be something more. The opening lines from the first I'm Alan Partridge had the reduced personality talking to the insomniac listeners of his show: "This is Radio Norwich, and that was 'Big Yellow Taxi' by Joni Mitchell, a song in which Joni complains that they 'paved paradise to put up a parking lot' - a measure which actually would have alleviated traffic congestion on the outskirts of paradise - something which Joni singularly fails to point out, because it doesn't quite fit with her blinkered view of the world. It's 4.37am, and you're listening to Up with the Partridge..."

If that's your idea of good comedy, here's the good news, as Coogan gives it to me. Partridge is to return, possibly at the end of next year. And he is no longer the chastened figure he became by the end of the last series. "He's come through his crisis," reveals Coogan, adding, "but only in the East Anglia area. We've had some new ideas: Alan on the Net, for example." Coogan's face changes, and he picks up an imaginary phone. "And Lynn, get me on the information superhighway. No, don't ask me questions, just do it."

He knows his characters very well. We are talking about how Partridge represented a reaction to Thatcherism ("It's all right, David," says Coogan, "you can use the word 'Zeitgeist'") and that brings me to Coogan's scary Mancunian, Paul Calf. I say that I can imagine the worrying Calf at an anti-paedophile demo. "Yes," Coogan agrees, "but he's there making money by selling banners to people."

Despite his seriousness, Coogan does not see himself as an intellectual, but more as an artisan. His characters and the nuances of their behaviour are painstakingly crafted, not created by sudden Cambridge Footlights acts of brilliance. All Coogan asks for is that they illuminate something: a situation, a type, a way of behaving. They should be more than just worth a laugh. Which is why he has nothing but contempt for some modern television comedy. "I don't mind saying," he doesn't mind saying, "that I can't stand the 11 O'Clock Show on C4. It confuses challenging with tasteless. Irony doesn't stop crap being crap."

Instead, he admires the BBC's The Royle Family for the risks it takes, for its "creative bravery". "You know the bit where the man sings a song in the living-room? And normally you'd only get a verse or two and some reaction shots. And they did the entire thing. It was brilliant." At first, he tells me, BBC executives had said that the idea of filming as if in real time would never work, it would be too boring. But like him, Caroline Aherne was cut some slack because of her track record.

For the last 18 months, however, he has been engaged, with fellow writer Henry Normal (who also co-wrote The Royle Family) on writing, rewriting and re-rewriting the film. He was determined to get it right. As a result, the script is now described by Universal as one of the best they have ever seen. Everyone associated with The Parole Officer is very up about it. I say it's a risk, given the history of British TV comics in the movies (apart from John Cleese, that is. And Michael Palin. And Lee Evans). "Not as big a risk as doing another sitcom," replies Coogan.

Coogan is unflash - far from the Ferrari-driving smoothie portrayed in the tabloids - and refreshingly earnest about what he does. There's none of that tedious refusal to talk sensibly about comedy, or that flip way of dismissing the pain that goes into good television and film. Not for him the claim that success comes effortlessly, that he got straight As in his exams without doing a stroke of work. He's the Gordon Brown of British comedy, a metaphorical son of the manse.

So I ask him if either of his parents are perfectionists. Yes, he says, taken aback slightly. His father, a computer engineer, is very much like that. Very deliberate, very earnest, very honest. And - I imagine - very good at computer engineering.