Some actors inhabit a role so perfectly that it can go on to haunt their careers — Christopher Reeve’s Superman, Harrison Ford’s Indiana Jones and Sean Connery’s Bond, to take three examples. With Viggo Mortensen, it will be hard to shake his barnstorming performance as Aragorn in The Lord of the Rings. He took a shadowy, unlikely hero from the pages of fairytale and created a fully formed man. The film was hugely successful, and he became a Hollywood playa.

So first, you have to get that out of the way. And a look at Mortensen’s career since Aragorn proves that’s pretty much what he’s been trying to do. In the five years since The Lord of the Rings, he’s chosen to work on five films: as Frank Hopkins in the man-and-horse epic Hidalgo; as Tom Stall in the political fable A History of Violence; as a 17th-century mercenary in Spanish-language adventure Alatriste; as a German professor resisting Nazism in Good and in David Cronenberg’s new thriller Eastern Promises, set in the underworld of the Russian mafia in London. Notice anything about those parts? Blockbusters they ain’t.

‘If I was interested in being as famous as possible and making as much money as possible, then I would have done things differently,’ he smiles. ‘But I find other things much more interesting.’ In Eastern Promises he plays Nikolai, a mobster covered from head to foot in tattoos. He researched the role so well that he knew how significant these markings are — they tell a gangster’s life story, where they’ve served time and what crimes they’ve committed. During filming, he found it troublesome to wash them off and reapply, and was once mistaken for a killer in a nasty London pub.

‘The tattoos were important to get right,’ he insists. ‘The film is about how things escalate, and asks the question, What atonement can there be for blood spilt on the earth? It seems very pertinent to ask that question now. Blair, Bush, Howard - what atonement can they make? My character, as it happens, is not violent,’ he laughs. ‘Which is different from most of the roles I’ve been given in the past.’ For a man who so often goes to war in character, his resistance to Iraq is very public — so much so that, in 2004, the conservative film critic Michael Medved attacked him in USA Today for his ‘pacifist preening’. He’s been known to send journalists anti-war t-shirts, and in August 2005 he joined Cindy Sheehan on the dusty road outside George W. Bush’s family farm as she protested her son’s death in Iraq. He brought gifts — fresh vegetables, bottled water and a copy of Animal Farm. ‘I just wanted to talk to her, to see what she had to say,’ he shrugs. ‘Besides, I figured Bush wasn’t going to come out any time soon, so she could use something to read.’

In fact, his other off-screen choices have been as curious and un-Hollvwood as his movie choices. He reads his poetry at a literary arts centre’s open—mic evening. In 2002 he started a small publishing company called Perceval Press with Pilar Perez, a curator at the Santa Monica gallery. It’s named after a character in the Arthurian legends who chose a hard path. They asked Dave Eggers for advice and he said, 'Be very hands-on and uncompromising in terms of content, design and distribution.’ It’s a lesson Viggo took to heart.

‘We make sure the authors are happy with every aspect of the finished work: editing, font, layout, type of paper, images. Writers are often pleasantly surprised that they have so much say. I tell them, "You’re not likely to get rich. To he honest, your book may not make a profit for quite a while. Rut I can promise it’ll be a book made as close to the way you have envisioned it as possible."'

His cooperative spirit led him to take a most unusual step in Hollywood — he organised his fellow actors in a dispute over pay. In 2003, New Line had fallen out with the cast of The Lord of the Rings over compensation for the months of promotion the actors were expected to do. Viggo spearheaded their collective negotiations, much as you’d expect from an old-school trade—union leader, although he’s not keen to talk about it.

Perhaps this behaviour is less surprising given his background. He was born in Manhattan to a Danish father and an American mother who met while skiing in Norway and who ever after liked to travel. He has spent more time in Argentina than anywhere else, where he learned to ride and fell in love with adventure stories. He decided he wanted to be a gaucho, a cowboy, but that ended when his parents divorced. He was 11, and he moved to upstate New York with his mother — to an America that was reeling from Woodstock and the moon landings.

He studied government and Spanish literature at St Lawrence University, then moved to Denmark where he worked as a waiter, bartender, longshoreman and baker’s delivery boy. His body is covered with scars as a result — one from dropping lead bars on his leg in a smelting plant, the one under his nose from some barbed wire and one or two from his youthful habit of getting into scuffles. The bohemian intellectual with a penchant for writing poetry found himself drawn back to America and ultimately Los Angeles, where he married Exene Cervenka, singer in punk band X, and secured his first movie role as an Amish farmer in Witness.

It may be that he picked up something of the Amish ways — he uses his TV to watch movies, only has a laptop for Perceval Press matters and for years even avoided owning a cell phone. ‘I would call in my messages from a pay phone on the corner near my apartment,’ he grins. ‘I might not check my messages for days, and I probably lost some jobs because of that. When I finally got a mobile, I threw it out of the window when it rang because the sound was so annoying. A neighbour rang my bell, asked me if it was mine and handed it back to me. I put it in the closet under a pile of laundry and a few days later it rang again. I didn’t like the intrusion so I tossed it out the back alley.’

He finally relented after pleading from his son Henry. Although Viggo and Exene split after they had him, the couple stayed friends and raised the child through constant consultation. Now that Henry’s 20, father and son are best friends. They go to the movies together and travel — even taking a road trip from New York to Los Angeles with so many diversions it ended up totalling 14,000 miles instead of 3,000. He admits, however, that the effect his own parents’ divorce had on him made him feel unhappy about what might happen to Henry when he and Exene split.

‘It bothered me a lot,’ he says. ‘It reminded me. But we have a good relationship and friendship. It’s good for Henry and it’s good for me.’ It wasn’t necessarily perfect for his career, however. Fatherhood meant taking work where he could get it — hence Leatherface: Texas Chainsaw Massacre III and the trashy psychodrama Prison.

‘Most actors can’t make any kind of living,’ he says slowly. ‘I’ve been lucky to make a good living for the last few years, and for several years before that to make a living of some kind, more or less. Sometimes I ran out of money, but then I found work. I’ve been really fortunate in that sense.’

It was Henry’s advice that made him take on Aragorn, and you sense that part of him remains ambivalent about the role — or at least, the temptations its success threw up. ‘Everyone in the main roles has had a time now when they could get huge roles,’ he says. ‘I would never have met David Cronenberg had it not been for The Lord of the Rings. I would not have been able to make my last five movies — not even the Spanish movie, even though I speak Spanish and look right.'

For all that, he finds the trappings of stardom absurd. He hasn't watched the Academy Awards since the 1980s, although he saw ten minutes at his brother's house a few years ago. He believes the opportunities and rewards of life lie elsewhere - and this seems an appropriate point to tell the legend of Perceval.

After taking the hardest route through the forest, Perceval comes to a castle at night. He is given shelter by the castle's owner and stays the night. He is woken from his sleep by a curious procession as the Holy Grail passes in front of him. Somehoe, Perceval remains silent and avoids the temptation to take the cup. In the morning he wakes up and the castle is gone - as is the grail. He returns to King Arthur's court where, that Christmas, a vision of the grail is seen. All the knights depart of a quest for the cup. Perceval travels with Galahad, the knight who eventually finds the treasure. Although Perceval gets to see its splendour again, it is Galahad who gets the glory.