David Schwimmer has parlayed that extraordinary success of Friends into a steady career in films, theatre and television. He tells Donald Clarkeabout going behind the camera to direct Simon Pegg in a British comedy

David Schwimmer, the lugubrious, faintly equine actor and director, is only very slightly late for his interview. Less bumbling than Ross Geller, the unlikely palaeontologist he played for a decade on Friends, but every bit as verbally hesitant, Schwimmer launches into an unnecessary explanation.

"I am sorry we weren't quite on time. We had to lose this paparazzo," he says. "I have all these manoeuvres that I use. Like here, we went into this coffee shop nearby and the car waited at the front for me. Then I snuck out the back entrance and ran here."

Really? I've always quite liked Schwimmer - people tend to forget that he was meant to be a bit of a schmuck on Friends- but I wouldn't have thought that he was still of interest to the snappers. Unlike, say, Jennifer Aniston, Schwimmer has had a fairly uneventful private life. He has, to my knowledge, never been seen snorting cocaine off Jordan's midriff. Why would they bother?

"I don't understand it myself. I don't think I'm really all that interesting. But it still happens. I don't let it affect my life too much, though. I still think I can live a normal life."

Simon Pegg, the star of Run, Fat Boy, Run, Schwimmer's second film as director, has described how, while shooting the romantic comedy in inner-city London, the poor man could barely buy a sandwich without being battered black-and-blue by autograph hunters. Still, despite the hassle, he has managed to put together quite a funny little film.

Run, Fat Boy, Run, which follows a layabout as he trains for a marathon to impress his estranged girlfriend, has a very peculiar history indeed. Originally written with a New York setting in mind, the script, following acquisition by a British company, has been convincingly transformed into a very English piece of work. Pegg, the writer and star of Shaun of the Deadand Hot Fuzz, was in charge of the rewrite and, sure enough, it has his comic fingerprints all over it.

"We originally had somebody like Philip Seymour Hoffman or Jack Black in mind," Schwimmer says. "Then it was bought by a studio here in Britain and I kind of lost interest. But I had worked with Simon on a film called Big Nothingand I felt that, as he is also a great writer, he might be ideal for it."

Pegg is certainly very funny in the film, but, as fans of Shaun of the Deadwill attest, he is far from being the world's fattest man. It seems odd that, after ditching the idea of chasing a rounder man such as Jack Black, they didn't jettison the title as well.

"We certainly discussed it," Schwimmer says. "After Big Nothing, Simon got into impeccable shape. He had done all this training and when I next saw him I barely recognised him. We thought about changing the title, but, every time somebody asked me what I was working on, I'd say Run, Fat Boy, Runand they'd immediately laugh. So we thought we'd keep it. It's not really about being fat, anyway. It's about psychological and physical laziness."

It's a sort of metaphorical fatness.

"Yeah, that's a good way of putting it."

Raised in Los Angeles by well-off parents, David Schwimmer, now 40, studied drama at Northwestern University in Chicago and, after graduation, helped set up the Lookingglass Theatre Company in the city. In 1994, by which time he had only managed a few minor roles on television, the offer came to appear in the pilot episode of some show about six shiny New York buddies. Did he have any inkling that Friends was set to become an era-defining phenomenon?

"Oh, none of us had any idea. It is never anything anyone can predict. You spend at least a year trying to get on a pilot and, even if you get one, you know the odds of that becoming a series are about five per cent. Then if it does get commissioned the chances of it getting past 12 episodes are tiny. So, yeah, we were excited, but we all expected to be back waiting tables in a few weeks."

As things worked out, the six actors became, for a while, the most highly paid television performers in the medium's history. Over the last 13 years, Schwimmer must have mused on the reasons for the show's galaxy-devouring success.

"It did reflect a new sense of family," he offers. "Kids were growing up and leaving home for college earlier and their friends were taking the place of family. Suddenly, it seemed that your friends were the people you went to for counsel and the show got that quite well."

Despite the inconvenient dives into coffee shops, Schwimmer admits that the benefits of stardom greatly outweigh the demerits. The prominence he achieved on Friendsenabled him to secure a role in Band of Brothers, a spell in London's West End and, lest we forget, an amusing recurring role in the fourth series of the great Curb Your Enthusiasm. Still, there must be times when he longs to walk down the street unmolested.

"There are days when I think, what if I just checked out? What if I grew a beard and went off to live somewhere remote? I have often wondered about the freedom that would bring. But, you know, the fact is that I love what we do in this business and there's nothing else I can do."

Run, Fat Boy, Runopens today. See film reviews.