Michael Fassbender has always wanted to be in a cowboy movie, so he leapt at the chance to reunite with first-time feature writer-director John Maclean. The two previously worked together for three days on the 2009 short Man on a Motorcycle, so Fassbender came on board Slow West not only as an actor but also as a producer.

Michael Fassbender and Kodi Smit-McPhee in 'Slow West'Michael Fassbender has always wanted to play a cowboy in a Western

Maclean wrote the role specifically for Fassbender, who helped develop the script before filming began. "It was nice to see that journey through," Fassbender says, "as this was an idea that he'd had brewing for a good few years."

Maclean was impressed by Fassbender's dedication to the project. "Michael is just so busy," he says, "he's always moving. There was a lot of discussion when the script was being written. Then once the script was set, he backed off so it felt like I was being left alone to do what I had to do."

Watch the trailer for 'Slow West' here

Fassbender plays the bounty hunter Silas in the film, and as usual put a lot of preparation into the role. "Silas is a loner who doesn't really have much in his life, in terms of love and companionship. And without much joy in his life, he's become a bit bitter and cynical," he says. "The introduction of Jay into his world infuses him with some feelings of hope and enthusiasm, and commitment to something other than money."

Played by Fassbender's X-men costar Kodi Smit-McPhee, Jay is a naive but tenacious 16-year-old who meets up with Silas as the film opens. "Silas can survive very well out in the Wild West," Fassbender observes, "but Jay is hopeless, and so the two of them get together and come to depend on one another."

More: Read our review of 'Slow West'

Smit-McPhee agrees: "It's a great dynamic between a young man and an older man. They end up growing toward one another and learning things from one another and switching roles in a really weird way, but I think that may have just happened naturally. Michael's character is in the Western world and through the tragic, brutal things he's seen, just to be with such a pure entity was probably really interesting for Silas."

Smit-McPhee goes on to say, "I really appreciate him as an actor. He's a child at heart, but in the most positive and honest way. He brings a great energy to set."