The film has been in the works for more than a decade, and its path to the cinema has been rocky. The first hurdle came with the casting of Idris Elba in the lead role, which sparked a social media outcry that the character isn't black. King himself weighed into this debate. "Honestly, I didn't care what colour he was as long as he could command the screen, draw fast and shoot straight," the author said.

Idris Elba and Matthew McConaughey in The Dark TowerIdris Elba and Matthew McConaughey in The Dark Tower

For his part, Elba was intrigued by playing a character from a King novel. "I was excited to sign on for the role because he does create complex, well-rounded characters with a lot of depth," the actor says. "And Roland Deschain in particular is a character that has a massive, massive journey throughout the book series. Yes, I want the fans to be satisfied by the character I portray, but the wonderful thing with being an actor in film is that I am able to interpret the character. And I hope the fans are proud of our interpretatiom.

To get into the role, Elba had to learn some new skills. "There was a lot of physical preparation," he says. "Roland is the last in the line of phenomenal, dedicated security guys that use guns, so I had to learn to do that really well. But my character is equally as tormented and has as much history as The Man in Black. We share a history."

The Man in Black is the story's antagonist, played by Matthew McConaughey. "Matthew and I only did two or three days together but we really bonded," Elba says. "Because of the way movies are scheduled, Matthew joined the film nine weeks after we started. What that meant was that I avoided seeing him until we had the scene where we meet for the first time, which was great for the actual chemistry on the film."

Over those days, the two actors spent a lot of time together. "He's super engaging, super real," Elba says. "It's a real collaborative process. Matthew is really open and warm, and really good to work with. Of course, he's also a wonderful actor. He brings real depth and a sense of humour to the character. He's a likeable bad guy."

Watch the trailer for The Dark Tower: