For a long while, he wondered why he’d bothered. He waited and waited at the designated rendezvous and only as he was about to disappear again, an hour later, did Incisor appear.

They walked and talked for a further hour and, although on this first occasion, Incisor still gave little away, von Braun was able to build a sufficiently strong relationship in subsequent meetings to winkle the truth – or the story the man wanted to tell – out of him.

Von Braun was naturally sympathetic. He needed no instruction on how tough it was to be gay in Russia and had heard many stories of prejudice and abuse – indeed one could argue that it was impossible to be gay here without one. Incisor’s father had been a former Soviet Army officer and vicious bigot, who had once beaten his son severely enough to require a hospital stay for the singular sin of wearing his mother’s lipstick.

After that incident, Incisor had done everything in his power to hide his sexuality for many years. He married an unkind girl, who quickly suspected the truth and took to taunting him for his inability to sustain erections during intercourse. Instead of leaving him, she decided to blackmail him to fund her prodigious shopping and gambling habits. Incisor drifted into white-collar crime and debt, in both cases with the kind of people you most wanted to avoid in Russia or anywhere else. His eyes glimmered with the kind of desperation that comes from knowing you’re only a heartbeat away from being discovered at the bottom of the Moskva river.

Von Braun made him wait. It was only on the fifth or sixth meeting that Incisor was terrified enough of impending doom to admit that he worked for the Russian Foreign Intelligence Service, not the Foreign Ministry. He withdrew again after that confession and almost ran for his car, but he came back the following week and on this occasion admitted that he worked in a section of the Travel Department that arranged logistics for the service’s most senior executives, including Igor Borodin and the operatives of Unit 61a, which Incisor said the (technically) former chief ran as a private empire.

By now, Andrew and Jilly were directly involved, consulting with Ian and Suzy in London. Ian signed off on a very expensive offer: the settlement of all Incisor’s debts plus safe passage, a pension, house and offer of employment in London, if he was able to complete two years’ service.

It was the kind of deal they gave only to a select few and Kate had wondered at Ian’s decision to sanction such expense. Was it just ambition?

Since then, Andrew said, the flow of intelligence from Incisor had been solid, if unspectacular. He had a good handle on gossip within the SVR, which was sometimes useful but largely provided confirmation or overlap of what they were hearing from other agents. He had been able to provide few details on the movement of Borodin and others because they had barely left Moscow in recent months.