What follows is a truthful account – in as much as any old spook is capable of being truthful – of my role in Operation Windfall mounted against the Stasi in the late 1950s and early 1960s that resulted in the deaths of Alec Leamas, the best secret agent I ever worked with, and the innocent Elizabeth Gold, for whom he gave his life. So it would probably help if you were to reread The Spy Who Came in from the Cold before starting on this.

You’re still with me, I see. No matter. If I have the nerve to completely rewrite one of the best cold war novels of all time, then chapeau! for joining in the fun. Chapeau. I can’t lose my French roots. My name is Pierre. Though you probably know me best as Peter Guillam, long time member of the Circus and one of George Smiley’s field men.

The letter summoning me back to London arrived this morning. Soon I was back in the monstrosity – known as “Welcome to Spyland Beside the Thames” – being interviewed by Bunny and Laura, two fresh-faced ingenues from MI6. “Do you have a mobile phone or an email address?” asked Bunny. I didn’t reply. Dead-letter drops and Remington typewriters were the only means of communication I really trusted. Bunny continued. There was a problem. Alec Leamas’s son, Christoph, was threatening legal action against Six over his father’s death. What could I tell them about Operation Windfall? Very little, I replied. Lying was still second nature.

“You’re going to have to do better than that,” Laura said evenly. “We know all about the Stables.” I suddenly felt very tired – unsurprising for a man who must now be in his mid-80s. Don’t ask for my exact age as it has been long forgotten. Call it Tradecraft.

I took them round to the Stables. It was exactly as I had left it more than 50 years ago. Same shabby furniture, same narrow staircase, same spooks reading dusty reports. “We have all the files,” said Bunny. “You may as well tell us the truth. Did you sleep with Doris, codename Tulip?”

“No,” I replied. Like so many things, it wasn’t quite a lie. We hadn’t slept together. We had made love on many occasions as she passed Soviet secrets to me. “I’d like to speak to George.”

“I’m afraid George isn’t around. He is well over 100, after all.”

I walked slowly home, careful to let Christoph tail me closely. I bent down to tie up my shoelaces and put my back out. “Give me €1m and I’ll drop the case,” he said. “I don’t have that kind of money on me,” I replied, surprised I could occasionally still tell the truth.

The interrogation started again the following day and continued for several weeks. My mind went back to Camp 4, where Tulip had been brought for interrogation. “She’s dead. Hanged,” George had told me. “But don’t tell anyone on Joint. This is strictly Covert only. We have a mole. Tulip was murdered by a Stasi double agent whom we’re planning on turning into a triple agent.”

Christoph appeared with a gun. I quickly disarmed him and threw the Walther into the Thames. “Go home,” I advised him. “You’re well out of your depth. Like the pistol.” I slipped away to find George holed up in Switzerland. “You’re looking good for one of the oldest men alive,” I observed.

“You too,” he replied evenly. He sighed. “I suppose you want the truth. It’s complicated, Peter.” It always was. “There was no triple agent. There was a quadruple agent instead. Fiction is a dirty world. Yes, you’d have thought that at least one of my books would have been recognised for a literary prize. But critics are worse than spooks. They lie to themselves and others. It’s second nature. We can tell better stories and write better prose, but we’ll never make a shortlist. It’s the way of the world, Peter. Get used to it. I have.”

Digested read, digested: The Spy Who Went Back Into the Cold.