Woody: The cops could nail me

Somehow he finds something sympathetic in the least lovable of rogues, making audiences like, and even root for, thoroughly nasty pieces of work: serial killer Mickey Knox in Natural Born Killers; sleazy David Murphy, who sells his wife for a night, in Indecent Proposal; pornography king Larry Flynt.

In The Night of the Iguana he does it again, playing T Lawrence Shannon, a disgraced Episcopalian minister, drummed out of his church for blasphemy and fornication.

Evening Standard's theatre critic, Nicholas de Jongh, gave Harrelson a rave review, describing a performance of great "emotional force and bravado".

"Tennessee Williams describes him as a guy who's caught between his belief and disbelief, and I guess I feel that too," he says. "I relate to him on many levels. His main struggle is with religion, and having grown up very religious and then kind of segued into a much different lifestyle, I do identify with something in Shannon."

Harrelson's life story would itself make an intriguing Hollywood movie. His mother was a fundamentalist Christian who brought up three sons as strict Presbyterians, first in Texas, then Ohio, alone and in relative poverty. "Pure white trash to the end," says Woody.

Remarkably, his father, Charles, who deserted the family when Woody was seven, is currently serving a life sentence in a Colorado penitentiary for the contract killing of a federal judge.

A one-time construction worker, Charles Harrelson had already served one sentence for murder when, in 1979, he was allegedly hired as a hitman by a cocaine baron to kill one of America's toughest judges.

Seven years ago, his actor son paid for defence lawyers to appeal the conviction for a second time, but with no success. It seems likely that his father will spend the rest of his days in jail.

Harrelson rarely talks about his dad, though they're still in contact. He visits his father in jail occasionally and telephones from "time to time", he has said.

"I can see it's an interesting story in itself. But the thing I don't like is when someone paints a picture, like, 'Woody had such a hard childhood because his father was in jail,' and so on. I mean, for God's sake; kids are not impervious to that kind of thing, but they're so much better able to adapt than people think. So I don't think I was damaged by that."

He acknowledges his father's early influence. "My dad hated smoking," he says. "When I was seven years old I was hanging out with dad and he had this girlfriend who smoked cigarettes. There was a pack on the table and I said: 'Dad, can I have one?' He was clever. He said: 'Help yourself, son, go on, smoke the whole pack.' Well, I wasn't very many in before I never wanted another cigarette again."

As a teenager, Harrelson thought he might become a minister and got a scholarship to Presbyterian college, but "only gave two sermons, both on the subject of faith" before dropping out and opting, almost by chance, for acting instead.

Until he was 21, he was "as straight-edged as you get". "I never took a drink until I was 21. Everyone I knew was smoking pot or drinking from their early teens, but I wasn't like that."

Nonetheless, he was eventually seduced by sex, alcohol and marijuana. At one point during his days on Cheers, Harrelson claimed to be picking up and sleeping with three women a day, a brag he later admitted wa s hyperbolic (though not by much). He was associated with Glenn Close and Juliette Lewis, his co-star in Natural Born Killers. No longer

God-fearing, Harrelson indulged himself without restraint - while publicly admitting that his life was "empty" and that he was searching desperately for something to replace the intense religiosity of his childhood.

To an extent, he says, he's still looking, though his lifestyle is much more mellow, and family-oriented, nowadays. "I still am very much on the search for what's right and good and just, and I'm still ensnared by guilt and self-condemnation at times," he says.

There is something distinctly otherworldly about Harrelson, an ingenuousness (much like Woody Boyd) that might be mistaken for naivety were it not for the calm thoughtfulness with which he answers questions. Dressed in a beige sweater made of hemp, he seems to lack the glitz or ego that defines other Hollywood actors.

Today it's eco-activism - in particular the somewhat esoteric promotion of paper made out of flax, wheat and other sustainable crops instead of wood - that "really ignites my passion".

He and Laura have a campaigning website, voiceyourself.com, and hope to bring environmentalists together to form a powerful "cartel" to oppose the petrochemical giants.

Interestingly, Harrelson sees his role as missionary, evangelical even. "I guess that's what I preach about now. Sometimes I'm preaching to the choir, and sometimes to people who really don't want a sermon."

Harrelson is an outspoken advocate of legalising cannabis, too, though it's not an issue to which he dedicates much time. "I've kind of become the poster boy for this, when there are so many more important things to talk about.

But yes, there's a level of hypocrisy that exists within governments about it, and I have to call bullshit when I see it. Tobacco and alcohol and various pharmaceuticals are all much more addictive than pot. If they're going to be hardcore about banning things, I say spread it out across the board. If you're banning something because it's harmful, then freaking outlaw McDonald's."

Does he still smoke it? "Sure. If the cops [in London] want to nail me they just have to find me on a Saturday night."

Saturday is the only night Harrelson allows himself any post-show down-time, he says. "But you have to go out on a Saturday!" Sometimes he'll nip across the road to the pub with the other cast members.

He's a big fan of the Century Club, a private members' venue just down Shaftesbury Avenue. "I like the vibe there. That's a good place." As a strict vegan (some days he eats only raw food), he's also partial to the seaweed salad at Nobu.

Halfway through the interview, an assistant appears with a large beaker of green gunk which Harrelson proceeds to drink through a straw. "This is a bunch of green veggies, like spinach, celery, parsley, kale," he says in reply to my screwed-up face. "It's really good for you. Especially the throat: opera singers drink this stuff."

Harrelson has what sounds like a delicate meeting after our interview, with the veteran director of the show, Anthony Page. The tough economics of the West End mean that The Night of the Iguana opened after just eight preview performances, and Harrelson - like the majority of the West End critics - thinks it shows.

He wants to trim the play and iron out a number of problems. "The first play I worked on was a Neil Simon, and he always did the same thing: he'd open his play in one city for a month, then take it to another for a month, and then take it to Broadway. He didn't rush it. You learn so much while it's running. I think this opening right here was just a little premature. I'm an ox by the Chinese zodiac and I just keep trudging along. I will not rest until this thing is as good as it can be."

The Night of the Iguana is at the Lyric Theatre, Shaftesbury Avenue, W1 (0870 890 1107) until 25 March 2006.