Sue de Groot spoke to the 'Lord of the Rings' star about his career-defining role in the new film 'Captain Fantastic'.

"Never work with children or animals." Attributed to American humorist WC Fields, this advice is often quoted by Hollywood actors. But not Viggo Mortensen. Viggo (easier to type multiple times than Mortensen) disagrees with Fields. Viggo thinks Fields was talking nonsense.Viggo has worked with animals, children, hobbits, elves and dwarves.In his latest film, Captain Fantastic, he plays bearded hippie Ben Cash, a father who teaches his six children to survive, hunt, climb and especially think off the grid. (They live deep in the woods and celebrate Noam Chomsky Day instead of Christmas, to give you an idea.)"I've had great experiences working with animals and with children," says Viggo, "but this was extraordinary."It is mid-afternoon in Los Angeles - midnight in Johannesburg - and Viggo is taking calls in his hotel room before getting ready for the US premiere of Captain Fantastic, which he will attend with three of the young actors who play his on-screen children.story_article_left1The other three are elsewhere, working on new projects - "already reaping the benefits of this film," as Viggo puts it, delight and pride in his voice.Captain Fantastic has nothing to do with comic books or caped avengers. It is a funny, thoughtful and immensely moving chapter in the life of a distinctly unaverage family. Viggo says he feels a certain kinship with the intense, idealistic Cash."He is one of the most complex, layered, emotionally satisfying characters I have ever been able to play. I admire his ability to communicate and his encouragement of free, open, equal discourse. That's a good principle no matter what kind of family you have or what your personal ideology is as a parent."I admire any family unit, no matter how strange or how 'average' it might be, that is founded on the practices of constant curiosity and complete honesty. I think that's healthy - it's just common sense."Captain Fantastic received a 10-minute standing ovation in Cannes and was "a roaring success" at the Sundance Film Festival, where it had its world premiere and where Viggo's filmmaker-actor-writer-musician son Henry, 28, was at his side."I was so happy to be sitting there next to him watching it," says Viggo. "He laughed and clapped and was moved by it. He didn't have to say anything - I could see he loved it. He's coming again tonight."Some of the survival skills Cash demonstrates in the film were familiar to Viggo. "I was raised both in cities and in the country [his early childhood was spent in Argentina] and my dad was raised on a farm in Denmark and taught me to hunt and fish when I was very young. We went camping, my two brothers and I, our family did a lot of that."As an adult I've also lived in the woods and I like it. I lived in the same part of North America where we filmed Captain Fantastic, so that was familiar to me, but a lot of the other things were not."He was relieved when the rock climbing scenes were over. "I have a fear of heights. Rock climbing is not something I would like to pursue, any more than I would jump out of a perfectly good aeroplane with a parachute. The kids were climbing around with no fear. It was unnerving." We disguise it, we avoid it, we put off thinking about it, but death will come, uninvited, when you least expect it The on-screen dynamic between Viggo and the children appears entirely natural. This, he says, is due to the talents of the young stars as well as the off-screen bonds that were forged."This was one of the best scripts I had ever read," he says."When I met [writer-director] Matt Ross, I said it would be impossible for anyone to make a bad movie from this script, but making a great movie would mean finding child actors who are incredibly intelligent, physically committed, and who, even the youngest of them, can make the audience believe they really know what they're talking about, because some of the concepts they throw around are complex and intellectually challenging."Ross and casting director Jeanne McCarthy involved Viggo in the auditions: "So I got a head start on getting to know the kids, as people and as actors. Before we started shooting we had a couple of weeks of a sort of camp, where we did martial arts, jujitsu, climbing. By the time we started shooting we already knew each other, had bonded, liked each other and were already having fun together."They also improvised music together, as they do in the film. "That was a non-verbal way to get to know each other," says Viggo. "The most important aspect of it is listening - you have to listen to the others to be able to play along, so that was very helpful."Viggo plays piano in real life (he also paints and writes poetry and some other stuff) but for this he had to learn the bagpipes. "It's a hard instrument to master," he laughs. "I enjoyed it, but what you hear at the end is not me - there was no way I could get to that level."story_article_right2Back on the subject of working with animals, he says he has kept many of the horses he worked with on films such as Hidalgo and Lord of the Rings. "They were all very talented actors," he says of the horses."I'd love to have kept these children too, but I don't know if their parents would be too happy about that . I don't think the kids would either, but the highest compliment I have ever received as an actor was when some of the younger kids called me 'Summer Dad'."As for that red suit he wears on screen, he says it was modelled on one from his own wardrobe. "The shirt was mine and I also brought along a red suit, but my suit was a little too glittery, a bit much, and they wanted a different cut."On the phone it is impossible to tell whether he is joking. His voice holds the same teasing lightness as it does when he speaks of the way Cash helps his children confront the subject of death."I think it's beautifully done in the movie, the way they speak about death. We have a tendency, for understandable reasons - fear of the unknown being the main one - to not even want to talk about death. We disguise it, we avoid it, we put off thinking about it, but death will come, uninvited, when you least expect it."• 'Captain Fantastic' is in cinemas on Friday..