The strangest meal Dame Stella Rimington ever had was soon after the Berlin Wall came down, when the senior members of Britain's secret services met their counterparts at the Lubyanka in Moscow. Having spent nearly 40 years Tinker Tailor Soldier Spying on each other, desperate for scraps of information, here they were walking through the front door of the KGB building. "We must have looked like something out of the zoo to them," she says, "and they did to us. We had only defectors' accounts of these people, and suddenly here they all were in front of us."
Was there, I wonder, a sudden sense of shared humanity, a celebration of the final thawing of the cold war?
"No, there wasn't," she says, with a quick laugh. "It was more like wild animals looking at prey they could no longer eat. They were in this highly disturbed state where everything they had taken for granted about the future no longer applied. But one thing was for sure – they were going to hang on to their own positions and power. [Boris] Yeltsin had put a professor in charge in the hope of democratising and modernising them. He didn't last more than a few months."
Old habits dying hard, the Russian intelligence services still followed the Brits around Moscow on that trip and when they had a private dinner they knew their conversation was being recorded and all the ham-fisted waiters were KGB men. "Suddenly we didn't care at all. There was a hysteria around the table so we all started saying various things that caused the waiters to twitch and raise their eyebrows. It was quite the weirdest day of my life."
Rimington, now 78, is recalling these events in the Red Lion and Sun in Highgate, a gastro pub not far from her London home. My recording machine is in plain sight on the table. I guess in retirement all working lives seem another country, but few can seem as foreign a place as that of the ex-head of MI5. She attempts to bridge that gap by writing spy fiction; the seventh of her novels featuring her young alter ego Liz Carlyle is about to be published. She lives mainly in the country, and as she says: "Sitting, as I was doing the other day, in Norfolk imagining someone in difficulty in the Yemeni desert is tremendously relaxing."
Rimington is a surprisingly informal and warm presence, giving hardly a clue in her manner of her former power. Others worry about her security, but she doesn't. If she does venture out for lunch it will almost always be to a gastro pub for which she is spoilt for choice near both her homes. She likes this one because it is "cosy, unfussy and they have kept the original fixtures" and orders decisively the asparagus and salmon with nicoise salad, and a glass of sauvignon blanc. "The nature of my career has made me wary of social things," she says. "Initially, there was the need to not tell people what you did. You would slightly dread the question because you know you would have to make up some story."
Did that come naturally to her?
"It did come quite easily. But you tended not to accept invitations, or cultivate wide circles of friends and I think I am still the same. I am quite reclusive by habit now."
She split up from her husband 30 years ago and, having raised her two daughters, has subsequently lived alone, which she likes. "Loneliness has never occurred to me," she says. "Certainly not when I was working. The fundamental secrecy of the job means that it is a cohesive family unit. You can share things with colleagues that you couldn't share with even your closest friends, which was strange I suppose. And of course there is an easy answer to loneliness: get a dog, which I have now."
The last time I knowingly sat down with a British spook was when I was approached by MI6 after university and had a couple of surreal job interviews in rooms with darkened windows off Pall Mall before it was mutually agreed I was probably not about to become our man in Havana. My abiding sense then was that you would need an unshakeable conviction that what you were doing was right in order to lead so double a life. Having led that life herself, I wonder if she ever doubted its purpose? She must consider herself a great patriot?
She finishes her mouthful of English asparagus. "I suppose so, a bit like Mrs Thatcher in that way – the way she was always talking about her country. I think that sense that we were trying to be on the right side was strong. That came from my father, who fought in the first world war and worked in the steel industry. I came from an era where there were clear-cut enemies. In the cold war we were facing another country that wanted to completely change our way of living and had nuclear missiles aimed at us. Plus there was a covert war going on, with subversive acts aimed at undermining western democracies and making us all communists. My patriotism comes from that. I thought our democracy was clearly worth defending."
Her father fought at Passchendaele, and was "never able to relax after that, a very uneasy soul, difficult to get close to". She joined the intelligence service almost by accident having followed her husband on a work posting to India, and taken up a clerical job in the Foreign Office. After that her mother's influence came to the fore: she had been a formidable coper, having to "prop him and us four children up". One of the things Rimington had to cope with, not long after becoming director general in 1992, was her cover being blown – not by the KGB but by John Major's government. She was to be the first spy to go public.
"MI5 had no press office, so I was on my own. From day one, newspapers, particularly the Sunday Times, got my home number and told me they knew where I did my shopping and who I had lunch with. There was talk of [accessing] my medical details. All of this was dressed up as in the public interest. They published a photo of my house with my daughter's bedroom window open to show how lax security was. It was all quite alarming."
When we have lunch it is after the Boston bombing, but before the Woolwich attack. She must feel relieved every time there is a situation like that where she is no longer the one having to help form a strategy?
"In a way, yes," she says. "But leaving the service [she retired in 1996] was a combination of relief and bereavement. There is a sense of loss that you are no longer at the centre of things. From the outside, I think the service is in a good place having prevented terrorist plots here for a long time. But one day something will happen. That is the worry that lurks in the heart of every director general all the time: is there something we have missed?"
As a surrogate for that sense of anxiety and responsibility, Rimington immerses herself in her writing. How close is her fictional spy to herself?
"It's not all accurate but it's a bit memory lane-ish," she says. "I think she has developed as a person through the books. Less spiky and more nurturing. When she first started she was obsessed with her boss and thought she was in love with him, but he went off with someone else. Put it this way: she is all the things I like to think I once was. Sparky and spiky. I let her say many of the things I thought but didn't always say about all the patronising male colleagues and so on."
By now Rimington has given up on a trencherman's portion of salmon, and waves away thoughts of pudding. She has an appointment to get her dog washed. Before we leave I suggest it seems appropriate that she should be reflecting now on so unlikely and fantastical a life in the form of fiction.
She laughs. "I thought of calling my autobiography A Life of Surprises. I thought I was going to be a county historical archivist and have children. It didn't quite turn out like that."
The Geneva Trap (Bloomsbury, £7.19) is published in paperback on 4 July
