We are in a very remote part. But I still go to London a lot."
One of his great friends in London, the former Lord Justice of the Court of Appeal, Sir Alan Ward, inspired The Children Act. Voted the "most human face of the judiciary" when he retired last year, Ward is warmly acknowledged by McEwan at the end of the book.
The novel centres around High Court judge Fiona Maye, who specialises in the Family Division and must deal with a case involving a 17-year-old Jehovah's Witness boy whose parents are refusing to allow blood transfusions that would save, or at least lengthen, his life. Simultaneously, she is grappling with a personal crisis which may be affecting her judgment.
"Alan read the book to check the details but it was more than that, really," explains McEwan. "This novel wouldn't exist without him. He told me of a case that he had presided over, concerning a Jehovah's Witness teenager. A year or two later when I told him I was going to write a novel based on what he had told me, but taking it far away from the actual case, I met him many times during the writing to ask him lots of details about how things work. I knew practically nothing about the law myself and I read his judgments. They are superb, really brilliant, very humane, sometimes rather witty."
Ward often closed his court sessions with the words "toodle-pip", but it's hard to imagine Fiona Maye emulating that sort of jolliness. "My Lady", as she is addressed, prefers to project an aura of cool gravitas, and is praised by her peers "for crisp prose, almost ironic, almost warm", much like her creator's writing.
From her busy bench, she has observed over the years the unhappiness warring parents inflict upon each other and their children. The cases she generally processes involve "routine wrangles over residence of children, over houses, pensions, earnings, inheritance. Wealth mostly failed to bring extended happiness," McEwan writes.
"Yeah, we don't shed too many tears for the rich," he says drily. "I sat in on various courtrooms and it is extraordinary the range of things, especially in the Family Division, that a single judge would have to deal with in a morning - mothers whose children have been taken abroad by the husband and they may never see them again, plus routine divorces and wrangling over life and death issues."
However poised Fiona may seem, she is struggling to maintain her focus because she is heartbroken, reeling from the shock of an appalling betrayal. The night before, on what was supposed to be a peaceful Sunday evening, Jack, her husband of more than 30 years, calmly told her he intends to have an affair, saying, "Fiona, when did we last make love?"
She can't remember - but he can: "Seven weeks and one day."
But, hold on, at that age, that's not long, surely? "Yeah, men of a certain age can get seized by a kind of panic," McEwan responds drily.
Jack's decision - he doesn't want a divorce, he just wants to have "one big passionate affair" - has derailed Fiona yet she must continue to behave professionally. She tells no one that he has moved out - he didn't even say goodbye! - and, as she walks to the courts the next morning, tries to get him out of his head by "playing to her inner ear a piece [of music] she had learned by heart": Bach's Partita No 2.
But then Fiona, an accomplished piano player, remembers she'd learned to play it for him as a birthday present. So there he is, back in her head. "The engine of self-pity began to turn" and she starts to reflect on her childlessness, "a story," McEwan writes, "best told at speed" in a quick survey of her career starting out as a law student to the day she took her Judicial Oath and she "knew the game was up".
"It happens," says McEwan. "In the case of someone who is moving up through this very enclosed world and a very ordered hierarchy, there comes a moment when she is elevated to the bench and she marries the law like women used to become brides of Christ. It still haunts her."
At this particular point in time, her lack of family makes her vulnerable when she hears the pros and cons of the Jehovah's Witness case, which is urgent, and decides to visit Adam, the boy in question, in hospital. She is instantly smitten. "It was a long thin face, ghoulishly pale, but beautiful."
Adam is smart and lively, despite his grave illness. As they debate his reasons for the rejection of the transfusions, and the awful consequences, she is deeply touched by his spirit. They end their time together with Adam playing her a song on his violin, a piece of music she knows well, Benjamin Britten's setting of the wistful Yeats poem Down By The Salley Gardens. Then she sings it to him. It's a song that reappears at a harrowing climactic moment towards the end of the book.
"That melody is lovely," says McEwan. "I suppose this was always the core, the crucial scene for me. When Alan Ward told me he had suspended court proceedings to cross London and sit at the bedside of this Jehovah's Witness, even as he was telling it, I thought, 'I've got to write this novel.' Now, when Alan sat by this boy's bed they talked about the thing that this kid was most interested in, which was football, which I don't have a great deal of interest in.
"I was thinking, 'What could I have instead of football?' I thought then that if I cannot make this scene work I can't make the novel work. Something has to open up between them but not be too spoken on both sides."
The problem is that the meeting of Fiona and Adam's minds has explosive consequences.
His life is saved, his parents are delirious with happiness, and Adam loses his faith. He transfers his need for psychological stability to My Lady. "The irony is that she has acquired a sort of lover, in a way," says McEwan. "But he is also a son. It is very innocent but then she makes a big mistake, she blows it. She gave him even more expectation."
Ian McEwan was born in Hampshire to a Scottish soldier father who eventually became a major, moving the family abroad to Singapore, Germany and Libya, before young Ian was sent to boarding school in Suffolk at the age of 11, an experience he has described as bleak.
He took an English degree at the University of Sussex, then studied for a masters in creative writing at the University of East Anglia under the tutelage of the great Malcolm Bradbury.
After moving to London in the mid-70s, he became part of a literary circle associated with the New Review magazine, and formed lifelong friendships with writers Julian Barnes, Christopher Hitchens and Martin Amis.
He also started to become known as a confident, original writer, with the publication of two books that earned him the moniker "Ian Macabre": First Love, Last Rites, a collection of short stories which included a tale of child sexual abuse, and The Cement Garden, about siblings who bury their dead mother in the cellar.
The Comfort Of Strangers (1981) was a menacing drama about two couples holidaying in Venice which was made into a film, as were The Cement Garden, Enduring Love (1997) and the Oscar-winning Atonement (2001).
The Comfort Of Strangers, Black Dogs, Atonement, Saturday and On Chesil Beach have all been nominated for the Man Booker Prize, which he won in 1998 for Amsterdam.
He once told an interviewer of his earlier writing: "I always used to deny this, but I guess what I'm really saying is that I was writing to shock ... I dug deep and dredged up all kinds of vile things, which fascinated me at the time ... [but] I've yet to meet somebody who said, 'Your stories are so revolting I couldn't read them'."
McEwan has two adult sons from his first marriage to Penny Allen, which ended in 1995. He has described his relationship with Annalena McAfee, a journalist, "as a very good marriage".
Aside from family and writing, the other constant in McEwan's life is his deep love of classical music, which threads through many of his books. It certainly plays a key role in The Children Act.
"I don't know what it is but seven-eighths of the world can survive perfectly well without classical music but I cannot," he says. "But there are pitfalls in trying to write about music. You have to stitch it into the drama. Sometimes I am reading a novel and I know the writer has some huge emotional connection to a piece of music but you cannot assume that in a reader. You've got to give it life outside of music.
"Music brings me a great deal of happiness. As you say, it has cropped up in my novels because it is such a big part of the furniture in my own consciousness."
He describes Fiona's piano playing so well surely he must play an instrument himself?
"No," he says a little mournfully. "I used to play the flute and I read music, I sing in choirs but these days I listen more than anything else."
Before talking to McEwan, I revisited the pleasures of a couple of his earlier books, including Amsterdam. A slyly comedic story of two old friends - a composer and a broadsheet newspaper editor, both giant egotists - who fall out and plot each other's murder, it includes a scene which is laugh-out loud. Vernon, the editor, has failed in his front-page bid to shame a politician and the paper's circulation is in free-fall. At a crisis meeting, a senior staffer says, "It's time we ran more regular columns. They're cheap, and everyone else is doing them."
The column ideas come thick and fast at the meeting: is my bum too big?; buying a guinea pig; I always get the supermarket trolley with the wobbly wheel; my first grey pubic hair.
McEwan laughs. "Well, opinion is very cheap. You just sit in an armchair and sound off. When I wrote Amsterdam columns of that kind were everywhere; now we take them for granted.
"But it was a new feature of newspapers, people just wandering on in no particular order or with any great intellectual spirit or incisiveness. Everything I took like 'why do I always get the supermarket trolleys with the wobbly wheels' or 'my first grey pubic hair', were all taken from real columns. In fact, one of the columnists who had written 'my first grey pubic hair' was introducing me at a festival and I just couldn't bear to tell him."
The Children Act (Jonathan Cape $36.99) is out now.
