Filming had already begun on The Lord of the Rings: The Fellowship of the Ring when Viggo Mortensen was brought in as a replacement for a rival actor to play the film’s sexiest role.

The key part of action man Aragorn—nickname, Strider—had initially gone to Ireland’s Stuart Townsend, star of small-budget films Shooting Fish and About Adam. But director Peter Jackson changed his mind and instead drafted in 43-year-old Viggo after the cameras had started rolling on location in New Zealand.

“It came as a shock,” says Viggo. “I hadn’t read any of the books and found myself on a plane, reading the script, trying to imagine myself playing this character.

“I’ve never before been in a position to do a job that another actor had already started. Although I was grateful for the role, I felt a little awkward about that. I never even met Stuart.

“It would have been much worse had he been my best friend or something. He’s much younger than me and the character of Aragorn needed to be older. It was just a casting miscalculation—one of those things that happen sometimes.

“I also had to look older than I am for some scenes and that would have been hard for Stuart.”

But Viggo, who has a 13-year-old son Henry by former wife Exene, threw himself into the part so much that he even wandered around the film sets on days off, barefooted and in costume.

“The director encouraged us to get involved,” he says, “so I ran around the place, in character. There was a gritty realism in that the cast were dirty, cold, wet and uncomfortable.

“I became hooked on the story, the character, the film sets and the atmosphere. It became so much part of my life that I still wear the ring I wore in the movie.”

But there were also doubts and worries: “I’d come to the project very late and worked hard, with little time off,” he says. “I became worn out and concerned about my ability to be up to the task.

“I was so tired that sometimes I was practically hallucinating. It was a good job that there was always someone else from the cast to help me out.”

Viggo, born in New York to a Danish father and American mother, is the hunk of the Ring in the new blockbuster and has a forbidden on-screen romance with Liv Tyler’s elf princess Arwen.

He had a good relationship with 24-year-old Liv. “She’s very relaxed and surprisingly mature,” he says. “She was so convincing, I honestly began imagining she really was an elf princess.

“As an actor, you learn to make the best of where you’re living and who you are with at the time. People like Liv were so warm and welcoming to me, it made the work a pleasure.”

In the past Viggo has filmed opposite other Hollywood leading women such as Gwyneth Paltrow in A Perfect Murder, Demi Moore in G.I. Jane and Nicole Kidman in The Portrait of a Lady.

“They all share the same quality of being disciplined and very driven,” he says. “Demi Moore was probably the biggest shock, because she never asked for any special treatment.

“She was having to do some amazing things as a girl soldier. She never complained, although I knew she was in pain and afraid of certain things. She never said anything, whereas the guys were whining and complaining on some days.”

He was equally struck by Nicole Kidman: “She never stopped working and getting inside her character’s head,” he says. “You look at some of these people and wonder why they’ve done so well. With Nicole, it was clear. She has all the talent, but never lets it get in the way of hard work. She’s also down-to-earth and could tell jokes very easily. The film crew fell in love with her.”

And Gwyneth: “A truly beautiful woman,” he reports.”Always in control. I played an artist who has an affair with her when she’s married to Michael Douglas. She was great to kiss.”

Viggo hasn’t been doing any kissing recently. He swears that he’s single, but reports that he still has a great relationship with his former wife, singer Exene Cervenka, of the punk band X.

“She’s an amazing singer,” he says. “If she was 22 and looked like Brittany Spears, she’d be on the cover of every magazine. She writes the most beautiful lyrics and has the best voice.”

Viggo is a poet himself, rather than a lyricist. His third poetry book will be published later this year. He’s also an accomplished artist and exhibits regularly in leading galleries in Los Angeles.

“I felt I had to do other things than just act,” he says. “That’s why The Lord of the Rings answered my desires. There was art, poetry and acting all in one role. Even if I live to be 100, I’ll never forget the thrill and the memory.”