THE film adaptation of Kazuo Ishiguro’s 2005 novel Never Let Me Go is one of this year’s most anticipated cinema releases.

There has already been a successful screen adaptation of the Golders Green author’s Booker Prize-winning The Remains Of The Day.

Now his futuristic sci-fi story, about a Norfolk boarding school where the students are clones intended to provide vital organs for “originals” or non-clones, is adapted for the cinema starring Keira Knightley, Carey Mulligan and Andrew Garfield.

The trio play best friends Ruth, Tommy and Kathy. Knightley is the opinionated, emotional Ruth, who strikes up an on-off relationship with isolated, bullied Tommy. Mulligan plays Kathy, the story’s narrator and the observer of the group, who seems resigned to her fate.

Mulligan, who made her name in Bleak House and last year’s An Education, which earned her a Bafta and an Oscar nomination, was already a fan of Ishiguro’s writing when she accepted the role.

“Never Let Me Go is my favourite of Ishiguro’s novels, but I love everything he’s written. It’s the lack of sentimentality and these unreliable narrators he creates – these people who can’t say exactly how they feel and so reveal themselves without knowing. Everything he talks about is so small and beautiful and detailed and never forces you into any sort of emotion but it’s completely overwhelming in spite of that.”

She adds: “I read Never Let Me Go in 2006. She’s 31 in the book and I thought, that’s really annoying, I won’t be able to play her for ages and if they do a film soon I won’t ever get to play Kathy because I genuinely wanted to play it from the minute I read the book. But they moved it down to 26 in the script – so it’s all worked out rather well for me.”

Mulligan says she approached the role focusing on her character’s flaws.

“She’s not a perfect character or a perfect narrator. I thought the mistake with her was to play her as morally upstanding level-headed and passive. I saw this documentary about a children’s hospice and there was this mother whose daughter was terminally ill and the girl was in her 20s. The interviewer said, ‘Do you ever cry?’ and she said, ‘I do go off sometimes and cry and I will cry one day but it’s not my day to cry yet.’ And that was the sense I got of Kathy, she’s not perfect or Mother Theresa but she does have an instinctive quality of caring for people and one day, when this is all over, when Tommy’s gone and when Ruth’s gone, that will be her time to mourn. Until then, she holds it together. She’s not a saint but she could so easily be a nothing. That’s why I’m terrified of her.”

Part of the novel’s emotional complexity is exploring the triangle of relationships – not just the relationship between Ruth and Tommy, but the love between Ruth and Kathy.

“It’s the idea of people growing up in an institution with no parent figures and how that affects you and how you form relationships with other people. But it is as much a love story between Ruth and Kathy, and Keira and I, luckily, are really good friends, so that helped. We’ve got a real connection, we have a shared history already and that’s what you come into, these people who have lived together their whole lives. Think how at ease or impolite or comfortable you are around your brother or your sister or your parents, that’s times ten with these people.”

The story makes intriguing points about how clones are perceived by the outside world and treated differently.

“Their language is kind of mannered,” says Mulligan.

“They have funny turns of phrases and, when they first come to the Cottages and glimpse the outside world, I think it’s more about how they’re perceived. When they go on a day trip to Norfolk, it’s how other people react to them and their discomfort with us.

“But we’re not playing autistic, weird children, because you do have to believe they do have souls – we do anyway – and that’s the question Kathy asks at the end, ‘Why would you ever imagine that we wouldn’t?’”

The film’s screenplay is by Alex Garland and the director is Mark Romanek, who worked hard to get his three lead actors to bond.

“The rehearsal process was for us to get to know each other, me and Andrew because we’d never met and Keira had never met Andrew, and for us to become much closer. Mark herded us all together and got us working on it and got us to a level where we could talk to each other really freely.”

Although a big star, Knightley was moved to accept more of a supporting role in the film because she believes subsidiary characters are often more interesting.

“I felt a little bit trapped by the notion that I was only meant to do lead roles. I was reading a lot of stuff and thought that the supporting roles were often very interesting and so I thought, whose rules am I playing by here?

“I wanted to play this role and find out what makes this person tick. I thought she was pretty reprehensible and I didn’t like her when I read it and I thought that was quite interesting. I wanted to know why that person behaves the way they do and try to understand why she became the person that she did.”

Knightley calls Ruth manipulative and cruel.

“I don’t like her. I don’t think I’d like her if I met her and yet I want to understand this because it’s important to understand how we can make horrendous mistakes and cause incredible harm. One of the wonderful things about being an actress is trying to get into the head of somebody who can do that and understand why.”

Knightley found the key to playing a clone was to see the trio as “a mirror to humanity”.

“Although they’re incredibly innocent because, obviously, they’re not allowed to have the experiences we take for granted, they are entirely human. They are institutionalised but, nevertheless, human beings.”

She adds: “Kazuo Ishiguro said an interesting thing to us, that actually it was about aging, which is very strange given that it’s a group of people who all die by the time they’re 30. But he said it was an analogy for the life span. They go through all the processes that we do in our lives, youth and middle age and old age, and yet it’s all condensed. We all face death, it’s the one certainty that everybody faces, and you can’t run away from it. It’s exploring that in the microcosm of this strange clone world, through the eyes of people who are not seen as humans.”

Knightley and Mulligan both met when playing sisters in Joe Wright’s movie of Pride And Prejudice.

When a film Knightley was slated to do fell through, and she discovered that Mulligan was a possible lead for Never Let Me Go, she jumped at the chance to work with her again.

“You rarely get opportunities to work with your friends and it’s amazing, particularly for actors, because it’s a very strange thing to do with your life and a very strange process. Very often on a film you don’t have rehearsals, so you’re asked to do these incredibly intimate scenes with people you don’t know. It’s wonderful that Carey and I have a six-year friendship and know each other very well. We didn’t have that thing of, ‘Is this a safe place that I can try to explore?’ It was instantly, ‘Let’s get down to work and have coffees and talk about this’, and almost bring our friendship and our own relationship into the dynamic between these two characters.”

Knightley enjoyed working with Andrew Garfield, who won a Bafta for Boy A and acclaim for his role in The Social Network and is due to play Spiderman in a Hollywood blockbuster.

“Boy A is a mind-blowing piece of work and his performance is just sensational. He’s hilarious and lovely and incredibly talented. We had a laugh and played Scrabble together. It was a very, very happy set and they’re not always. It was really nice that it was a very supportive atmosphere.”

o Never Let Me Go (12A) is out in cinemas from February 11.