Recently, John le Carre found himself sitting in the bleak banality of an old Stasi interrogation room in Berlin. It wasn't much to look at: small, peeling linoleum, plain furniture. The horror comes from imagining the psychological torture inside those walls a generation ago.
Le Carre went to the headquarters of the secret police of the former East Germany to remind himself. Partly he wanted to check details - he hates those smug letters from readers informing him that, for example, the church in his latest novel should have faced west. For the same reason he tracked down the old Berlin safe houses he remembered from his time working for MI6 in Germany in the '60s - one he found ("much tarted up"), the others he had to go to the old Stasi files to track down, much to his amusement.
But at Stasi HQ he wanted more than just geography.
"I had time alone in those horrible little rooms," he says. "It gave me back the smells, and the fear. And also - which can easily go missing - the justification for what we did. Because this was a foul regime."
This trip down nightmare lane was not for old times' sake. Le Carre was researching his new book, A Legacy of Spies.
It's a companion piece to The Spy Who Came in from the Cold and Tinker Tailor Soldier Spy, revisiting and (literally) interrogating the events from those two classics of spy fiction. Peter Guillam, loyal lieutenant to the legendary George Smiley, is called to account over their old schemes by a new generation of spies for whom the Cold War is a story, not a life's work.
Smiley has a small part - though one much focused on in pre-publicity thanks to his Europhilic attitude in a time of Brexit (le Carre: "an American journalist asked me did [Smiley] always feel so deeply about Europe? I said 'he does now'.").
Le Carre in person is everything you'd want him to be: a master storyteller with an apparently infinite supply of enthralling yarns. Over a Hampstead pub lunch, generously sitting out an England cricket win over the West Indies, he willingly grasps every conversational turn and runs with it, and refills your wine glass as he does so.
His pink shirt under a green woollen waistcoat conveys just the right touch of eccentricity, the gold ring on his little finger tells you discreetly that he's done quite well out of this spy book business, and his huge white eyebrows dip up and down as he speaks.
Some authors will tell you their novels were inspired by a dream, or a chance thought, or a stroke of inspiration. It turns out that Legacy came out of a failure of imagination.
In early 2016, the six-part TV adaptation of The Night Manager went phenomenally well. It rated across the world, the critics loved it, it won swags of awards. It was a huge commercial success. And the industry wanted more.
"Everybody was pressing money on us," le Carre says, "us" being him and his sons, Stephen and Simon Cornwell, who were executive producers. "Already AMC and BBC were saying 'what's next, how do we catch this wave?'."
So they started working on an adaptation of The Spy ... but immediately they hit problems. The first challenge for screenwriters was that the novel is "in effect, a film noir" rather than a mini-series, le Carre says.
So to expand the narrative he started building a new superstructure around it: background to the main characters, children and parents, extra facets to their secret lives. "I went on developing the notion of the past coming back to accuse the present in these people," he says.
But then they hit an insoluble problem: you couldn't start the series without the climax of the original, and once you'd shown that the series had nowhere to go.
"There isn't a last episode," he says. "So we put it all aside, we agreed - we'll think about it more and do something else in the meantime. So they've taken another of my books (instead)."
Le Carre won't be drawn on which one. But, he says, after they decided to move on "I thought 'actually we've gone over some very interesting territory here, and I think I'll write it'."
And that was A Legacy.
In an unexpected twist, the book caused le Carre's own past to come back to haunt him. He had agreed to a BBC documentary on the book - but then got cold feet, regretting the amount of time it required from him.
Before the project foundered, though, the BBC had, with le Carre's permission, applied for his Stasi file. It turned out to be "an absurdity" - press cuttings and a family folder - and it had been redacted by an unknown hand. And it had curious omissions - the fact he had been a member of the British embassy in Bonn (as an undercover agent), for example.
Then he heard "on the grapevine" that there was a file on his father, so he authorised the search for that. And it turned out to be extraordinary, he says.
Ronnie Cornwell - le Carre's real name is David Cornwell - was a confidence trickster who beat and then abandoned his son, and whose dodgy schemes spanned the globe. It appears that he even tried to con the Stasi - with whom he worked as an illegal arms dealer in south-east Asia.
"What he seems to have done is announce himself as a sympathetic businessman whom they could perhaps use as an intermediary," le Carre says. "There is a first description of him as a very rich Englishman, which is terribly funny because he was always deeply in debt."
A Stasi agent is dispatched from Vienna to Ronnie's office in London's West End - and comes back with a detailed diagram, including the position of the telex machine and safe. "That reads just like a reconnaissance before a secret operation, a burglary or whatever," le Carre says.
But unlike in his novels, he has no satisfying revelation to wrap up the story. "It's a mystery. I don't know what it means."
Le Carre has said he based Smiley partly on a college tutor (though mostly on John Bingham who sat near him at MI5, the domestic secret service). But there are elements of him in there - he is school-masterish and morally pained.
Of the world today, he complains that "we decent people are all mystified and joined by fear at the moment".
"We have more competing power blocs than ever, we have (China), we have something absolutely sick happening in the United States, we have something similarly sick happening in the former Soviet Union," le Carre says. "We have a convergence of hostility upon social democracy, human decency as we understand it."
In Trump and Putin (whom he pronounces Poo-teen) he sees "a convergence of autocrats" that cannot be good for the world.
The reviews of Legacy, which he does not read, have been generally positive, but some have wondered if his Cold War reminiscences are getting less pointed as time passes. But le Carre sees something very familiar in Putin - yet another "Chekist", named after the Cheka, the Soviet Union's first secret police.
"The KGB, now the FSB, these people saw themselves as a separate elite," he says. Russia still scares him - though "no more than it did". "Really the transition from tsarism to communism, from the golden tsars to the red tsars to the grey tsars has not produced a fundamental social change. The ascent of Putin completely re-established the power of the intelligence community, which is overarching now."
Burger toyed with and ice-cream finished, le Carre finally lets himself relax, as if he's shrugging off an unwelcome burden. He says: "that's the end of my promotion journey", a painful month of interviews in the press, TV and radio.
Le Carre wants to return to his next book, which he has already started. It's not about Smiley or Guillam or the Circus - "no, they're all finished with; that was the swansong for all of them".
Instead he's going on holiday, and: "Then back to writing and, as far as I can see, never another interview."
He doesn't enjoy publicity - "it's not really my taste at all to behave like that". "All the time I have ringing in my ear 'whore, whore'."
The way he describes himself, it's almost as if the master of deception is one of his own creations. "It's unnerving. You create an exterior perception of you, which is quite different to the way you see yourself. And then you either go mad and you accept that external vision - or you sort of fall into the gap."
Can we believe anything he just told us? Or was this all a deception, a double cross, where each side thinks they are getting what they want, but one opens their notebook later to find nothing at all?
It's the perfect le Carre ending.
A Legacy of Spies is published by Viking at $32.99.