The director of Never Let Me Go, which opens the London Film Festival tonight, talks about speed bonding with his cast, his love for Kazuo Ishiguro’s novel, and having a “vision with margins.”

Chicago-born Mark Romanek was a successful music video director (working with the likes of Johnny Cash and Nine Inch Nails) before making 2002’s obsession story One Hour Photo starring Robin Williams. He takes on a very different project with the screen adaptation of Kazuo Ishiguro’s lauded novel Never Let Me Go, the devastating story of three friends — played by Carey Mulligan, Andrew Garfield and Keira Knightley — who have a difficult life set out for them. Screen spoke to Romanek in Toronto; Never Let Me Go kicks off the BFI London Film Festival tonight.

Was it hard to take responsibility of bringing such a beloved book to the screen?

I felt such a deep affinity and love for it, and I saw it so clearly in my mind, that I didn’t feel that daunted by it. The day I did feel daunted was when I had screened it for Kazuo for the first time. We were pacing nervously outside the screening room and we walked in, took a big breath, and he turned to us and he had tears in his eyes and he smiled and said, ‘I love this film.’ He said, ‘I was watching it without even thinking of the book. I just got swept up in these characters. I realised perhaps in retrospect that I was quite worried about it but I surpressed it just to get the job done.

What was your rehearsal process like with these actors?

I didn’t have to talk to the actors a lot during the shooting, I tried to stay out of their way. But the rehearsal [for about two weeks] was the place where we all got on the same page about the film we were making. I tried to help the young actors get to know each other, bond with each other, and have there be some sort of spillover with the younger and older. I had the older actors read all the scenes that are played by the 12 year olds, which I think was a good idea because it helped the older actors have a sense memory of those moments. And it was a way to get the younger actors to see what more experienced actors would do with these scenes.

I also art directed the rehearsal space, I had my production designer dress and prop the rehearsal space. I played music, I had a plasma screen set up with photos of all the locations, we had a wall of reference photos and wardrobe props. There was a sense you were already immersed in this world, the world they were about to inhabit.

They had field trips. We spent a lot of time trying to bond – speed bonding – because the world of English boarding school is so hermetic, those relationships are so close, we needed to try to recreate that in a shorthand way.

Was it harder casting the younger actors?

My casting director did a spectacular job of finding these kids for us. It was a given that they had to be terrific actors, they had to carry the first 20 minutes of the movie. But I was very rigorous also that they had to resemble the older actors.

Nancy saw thousands of kids, it took months. We didn’t end up casting until kind of late. She didn’t even know who she was trying to get them to look like for most of the process.

Izzy Meikle-Small (who plays young Kathy) hadn’t been in front of camera. And she carries that first act beautifully, and has to believably hand the film off to one of our finest young actors [Carey Mulligan]. It’s a tall order. She really pulled it off, all three of them did.

With something like the colour palette of the film, how did you share your initial ideas with the team?

It’s a process, you try to communicate clearly the idea of the film to everyone, using words and images and other films. You just start the process where you’re trying to get everyone’s contribution to harmonise. You have to have a vision of the movie, but I say it’s like a vision with margins, because you are also incorporating other people’s contributions that might enhance the vision or take the vision in a different direction.

The music also added a lot to the mood. How did you decide to work with Rachel Portman?

I admired her scores. The trick with that score was that Ishiguro’s writing is very restrained and he didn’t push emotions. So we couldn’t have a score that was telling you how to feel, telling you to feel sad. And yet I wanted it to be beautiful and romantic. Rachel Portman seemed like the perfect choice to make a romantic score that wasn’t sentimental or pushy. It was a tightrope to walk.

This has such a different sensibility than One Hour Photo. What kinds of films will you make going forward?

I want to make lots of different things. One Hour Photo was something I was interested in getting out of my system then, and now I had the opportunity to adapt this novel by one of the greatest living writers, so I’m going to grab that job and go for it. I have a lot of affinity for this sad beauty in this film, and you don’t see that too often. I have other things I’m trying to do: a black comedy, a rollicking period adventure piece. I want to try to do lots of different things, I don’t want to get pigeonholed. My [music] videos were kind of all over the place and I’d kind of like my movies to be all over the place too.