When he was 17, David Duchovny had an accident that changed the way he looked. He fainted, standing in a lift. He hit the wall, and then the ground. They never figured out why - they put him in casualty and checked his brain and his heart, but it was all okay. He's never fainted since.

One tooth was knocked out right away, and they jammed it back in. One was chipped in half. One was twisted sideways, pushing his lip out. It didn't bother him much at the time - he was more upset about missing the next week's basketball game. He went around like that for two or three years, his teeth mangled. "I think maybe I smiled less," he says. Eventually he lost his top four middle teeth. It didn't freak him out until he became an actor. "I went, gee, I kind of wish I had my teeth," he says. "Just because they get so big up there on the screen, and sometimes I'm thinking people are looking and thinking that they're phoney."

Duchovny is now 37. He was not famous before he took the role of agent Fox Mulder in The X-Files, but he had enjoyed a quiet, semi-successful career ever since he gave up academia (he studied literature at Princeton and Yale) for acting. His most notable performances had been in the cult drama The Rapture, and, with Brad Pitt, in the serial-killer road movie Kalifornia, but there are little pieces of him littered all around the world's video stores: as a baddie in the canine high-jinks comedy Beethoven, as a transvestite detective in David Lynch's Twin Peaks, and as a cameraman in Richard Attenborough's Chaplin.

Naturally, though he appreciates what a godsend The X-Files was - and how well the character of Mulder suited his natural dry, understated style - he has also worked to keep his dignity, and his distance, from Fox Mulder. Neither he nor co-star Gillian Anderson had ever succumbed to the temptation to appear before their fans at an X-Files convention until Anderson recently cracked. When I ask him whether they pay good money for her to appear, he replies, evenly, "I mean, all money's good money, right? I'm sure that money was no different from the other money she had laying around." He still refuses to play along. "There's a certain merchandising aspect about it that I don't like," he says. "I'm not saying I'm Mr Integrity - I do my share of whorish things. And I'm not even saying that conventions are shamelessly ripping people off. But I didn't want to be involved in it."

He is well aware that some of the show's fans consequently think of him as ungrateful: "Unfortunately, the possibility is that they see me as being aloof. My feeling is that I make the show, and that takes so much time and so much energy, and that's a gift, even though I'm compensated for it. That's my gift to the fans and that's where I'd like it to end."

To change the subject from whoring oneself, I say, you're also known in Britain for your car advert. He smiles. It was a shadowy, faux-X-Files spot for Ford cars. "Why do it?" he mutters, before I ask. "Money. It's simply for the money. And there's something deeply wrong about it if you come at it from an artistic point of view." A wide grin. "And yet I'm able to live with myself."

If I remember right, you seem more Mulder than Duchovny in the advert. Did you mind that? "No," he says, "actually I preferred it to be that way. Rather than 'This is David Duchovny for Ford'. I'd prefer to whore Mulder than to whore myself." Incidentally, he does not drive a Ford.

He is married to American actress Téa Leoni. They recently moved into what I call a Malibu "mansion". He gets defensive."It's not a mansion. It's got two bedrooms." It is, none the less, a two-bedroom house in which you can lie in the bath and look at the Pacific Ocean. "So," he says, "you feel like you're floating in the water, above the water."

Téa Leoni stars in Deep Impact, one of the summer's other big-budget movies. When I ask him whether they had a domestic bet about whose movie would make the most money, he says, frankly, "I never thought there was going to be a contest. I thought we were going to crush Deep Impact, and now I think they're going to win. They've made $140m, and I don't know if we're going to do that." It was because of his marriage that he announced last year that if The X-Files remained based in low-cost, Vancouver he would refuse to return. His last few months in Vancouver were marred by a barrage of hostile publicity. The Vancouver media took his determination to be with his wife in Los Angeles as a rejection of their city. In the TV show's final episode of the fifth season, 15,000 people appear as the audience for a chess match; he was asked to attend and say a few words. It went fine, but he regrets doing it. "That's not how you say goodbye," he reasons. "It's like a show-business way to say goodbye. So I hated it."

Over the past few days, Duchovny has been traversing Europe, answering over and over pretty much the same questions he has had to answer in America. "It's very tiring," he concedes, cheery but slumped low in a London hotel-room armchair, "and there are moments of utter dread and self-hatred." In Germany he was momentarily diverted when a woman snuggled down to talk to him and began, "I know you are a big enema lover and I too am a big enema lover . . ." Crikey. "I was, whoa, I didn't know we were doing those kind of interviews," he says. Sadly, it was the accent. Animal-lover. She wanted to know about his dog.

Duchovny's stay in London is brief, but he has been trying to plug into the local culture, to observe and understand. "What do you think of Beckham?" he asks. He needs other, tangentially related information as well. "What," he asks, "does 'tosser' mean?"

One of the stories that did the rounds before it was announced that The X-Files was moving to Los Angeles was that the intransigent Duchovny was simply going to be replaced by a younger FBI agent, played by a Canadian actor called Chris Owens. He says that was never true. Ironically, however, he had suggested that Owens - who had played a couple of other minor characters - come into the series as a younger Mulder, figuring that it might help to get the older Mulder some time off.

"I would like it to become an ensemble show," he says, "so that I might have time to do a project while I was doing The X-Files." In truth, he would like more than this. "I would like to be off the TV show," he says, "but I'm committed to do two more years." After that, an X-Files movie every few years would nicely feather the pension nest for him.

Would you say categorically that you will not sign up to do longer than the two years?

"Oh yeah. Well, they might take my mother hostage and put a gun to her head. I don't think I should say categorically, but short of that . . ."

He will not now be able to make a non-X-Files movie until next summer. Whatever else he decides to do, he scoffs at the idea that he is under much pressure. "I've made it. I've made plenty of money - I'm not extravagant. I am proud of the job that I've done. I've done some films that I'm proud of. I've done a TV show that I'm proud of. I've attained cultural icon status, if that was something I ever wanted - no - but I can put that on my CV if I ever go for a job at Burger King. So what do I have to prove?"

He is once more explaining that he won't do something or other "unless they hold a gun to my mother's head", and, when the publicist interrupts, I am accusing him of harbouring a repressed matricidal desire.

"No doubt," he says to me. "Do you want me to pay you for that insight, or are you giving it to me for free?"

"Hmmm," says the publicist to both of us. "Matricide. Nice conversation."

"Your greatest literary achievement would be nothing without it," Duchovny points out. "Hamlet was the king of mother f***ers and killers. Yet you blush at the mere mention of it. You hypocritical nation. It's got a place in the theatre, but not in normal discussion . . . That is why you have such a wonderful culture. What is more inspiring than hypocrisy?"

It is soon after this that the nice, surprising Mr Duchovny is led away.

Heath, Chris. August 9, 1998. The Sunday Times UK.