Smash hit

But he was certain the invasion was going to happen anyway. “When it did I fervently wanted it to succeed even though a big chunk of left liberal opinion really wanted it to fail.”

Far from feeling slighted by Blair that day at the Tate, he was struck by “the helplessness of power. You’re wheeled around, you are introduced to the press and then someone says from the front door ‘Tony, you’ve got one minute’.”

Without giving away the ending of Saturday, the reader is left relieved as horror is avoided. Once that would have been unimaginable, McEwan’s novels being characterised by damaging sexual relationships and sadistic violence.

“One of the resources available to me is that I know my readers. They think it highly likely that something far worse than they can imagine is about to happen,” he says. And for once, it doesn’t. “I got interested in the idea of a man who thought he was extremely lucky because the woman he loved also happened to be his wife and (because this is so rare) he was actually troubled that he was a freak of nature: ‘hey, there must be something wrong with me ’.”

To write about a neurosurgeon, McEwan spent a year watching one at work, even in the operating theatre. Imagine coming round from brain surgery and staring into McEwan’s eyes, realising that macabre brain was taking an unnaturally close interest in yours. “I thought I would faint, but actually I was all right.” Instead, McEwan focuses on how humdrum brain surgery is for its practitioners, who chat about mortgage tax relief and what music to saw and chisel to.

“It is amazing how work is sorely missing in literary novels. People don’t seem to have jobs; they’re having affairs or having a terrible time with teenage children. You have to look to Kipling to find a real celebration of work. I thought, ‘Whether he’s going to be a shipbuilder or an architect, I’m going to enter this world, watch and absorb’.”

As a slushy pop song simpers away in the bar of a London hotel, he agrees that unhappy marriages have always been thought to be easier to write about. As he puts it in the novel: “For the professors in the academy, misery is more amenable to analysis: happiness is a harder nut to crack.” But McEwan saw this as a challenge.

“I thought, why not devise a character who actually is happy in his marriage, loves his work, gets on with his children and then finds what’s left to trouble him: the world outside. There is plenty of anxiety in the book, but there is also a celebration of cooking, wine, sex, love, children, work.

“We can be desperately, genuinely concerned about the misery created by the tsunami in the middle of the Indian Ocean, then 20 minutes later we’re having a nice time drinking a glass of wine with a friend. These things go in boxes.”

McEwan talks about his children — now grown up — with such affection they seem to be the central loves of his life. When he tells me how lucky I am to have small children he says so with passion. Still, he concedes he is now freer to travel and has moved from north Oxford back to north London.

Recent operations on both knees have filled his head with morbid thoughts about impending decrepitude and — worse — losing at squash. He writes: “Here’s how it starts, the long process by which you become your children’s children. Until one day you might hear them say, ‘Dad, if you start crying again we’re taking you home’.”

Perhaps McEwan sees it from both ends. He says that as his mother’s dementia worsened, visits became excruciating. “As soon as you left she would not remember you had been. It is very painful.”

Who needs wars when there is that much anguish at home? Does he think any real people are as happy as those in his novel? “No, if only,” he smiles ruefully. But McEwan, at last, seems to have come as close to happiness as we are ever likely to get — to a state of acceptance. And far from weakening his work, this has lent it a refreshing sense of humanity. If Blair really learnt to appreciate McEwan’s work, it might make him a better human being.

jasper.gerard@sunday-times.co.uk