'Bernard must not know,' said Fiona.

'Why?'

'For all kinds of reasons: he'll worry and give the game away. He's not good at concealing his emotions. You must know that.'

He looked out of the window. Fiona had chosen her man well. Werner had always wanted to be a secret agent. He yearned for it as other people crave to be a film star or score goals for their country or host a chat show on TV. Werner knew about espionage. He read books about it, clipped newspapers and memorized its ups and downs with a dedication that bordered on the obsessional. There was no need for him to say yes; they both knew that he couldn't resist it. 'I still can't believe it,' he said.

The driving school car came into sight as it turned the corner. It slowed and stopped, the driver carefully indicating his intentions with unnecessary signals. 'I think we should go,' said Fiona.

'I'll do it,' said Werner quietly.

'I knew you would,' said Fiona as she started the engine.

She overtook the driving school car and turned as if heading back towards Mahlow. It was a silly precaution that meant nothing. 'You're a brave woman, Fiona,' said Werner suddenly.

'No one,' said Fiona. 'Sir Henry and no one else unless he authorizes it to you personally.'

'How long will it go on?' said Werner.

'One year; perhaps two,' said Fiona.

'I thought they might make me persona non grata,' said Werner. 'I was worried about my work.'

'You'll be all right now,' said Fiona. 'It will be a perfect set-up.'

'Bernard must not know,' said Werner. The idea of having a secret from his best friend appealed to Werner. One day he'd surprise Bernard. It would be worth waiting for.

'Let me tell you what to say when we get back to the office. You'll see a Russian KGB colonel named Moskvin. Don't let him bluff you or bully you. I'll make sure you are okay.'

'Moskvin.'

'He's not a long-term problem,' said Fiona.

'Why not?'

'He's not a long-term problem,' said Fiona. 'He is being got rid of. Just believe me. Now let me tell you how we're going to handle this business of your reporting to me.'

Two days later the exchange took place: Erich Stinnes went East to resume his work for the KGB while Werner Volkmann was freed and came West. The KGB inquiry into the treason of Pavel Moskvin sentenced him to death. The court decreed that verdict, sentence and execution must all remain secret: it was the KGB way of dealing with its own senior personnel. The local KGB commander – a general who had been a close friend of Moskvin's father – decided that 'killed in action in the West' would be merciful and expedient, and so arranged matters. But Moskvin did not accept his fate readily. He tried to escape. The resulting exchange of fire took place on the abandoned Nollendorfplatz S-Bahn station in West Berlin, now converted to a flea market. Moskvin died. Bret Rensselaer, demonstrating his loyalty to the Crown, led the chase after Moskvin and was shot and hurt so seriously that he never resumed his duties in London.

The official British version of the events is very short. It was drafted by Silas Gaunt, who omitted any mention of the exchange of men because neither was a British national. It says that Pavel Moskvin – a KGB colonel on official duties in the West sector of Berlin – ran amok in the flea market. He fired his pistol indiscriminately until the Berlin municipal police were able to subdue him. Two passers-by were shot dead, four were injured, two seriously. Moskvin turned his own pistol on himself at the moment of arrest.

The secret file compiled by the West German government in Bonn had the advantage of detailed reports from both the West Berlin police and their intelligence service. It says that Moskvin was part of a KGB party who'd come West to arrange the exchange of a West German and a Soviet national held by the British SIS. This account says that Moskvin's death was an execution carried out by a KGB team which used two motor bikes to follow Moskvin's car. While it was halted on Tauentzienstrasse, near the KaDeWe department store, an accomplice threw a plastic bag filled with white paint over its windscreen. Moskvin left the car and ran to the S-Bahn station, shooting at his pursuers. At this time civilians were injured by gunshot wounds. When Moskvin jumped down from the platform to the train tracks, perhaps believing he could run along the railway and across the Wall, he was shot dead by a round fired from a Russian Army sniper's rifle. The perpetrator was never found but is believed to have been one of the KGB hit team who'd been seen coming through a checkpoint earlier that day. In support of this theory it is pointed out that there was never a request for Moskvin's body to be returned to the East.

A few days after the shooting, an unofficial mention of the body by British contacts brought from the Soviets only puzzled denials that any Colonel Pavel Moskvin had ever existed. There was no post-mortem. The body was buried at the small cemetery in Berlin-Rudow, very near the Wall. It was at this time that the Russians spontaneously offered to return to the West the remains of Max Busby, an American shot while crossing the Wall in 1978, Some inferred that it was part of a secret deal. Both bodies were buried at night in adjoining plots. It was at the time when the new drainage was being installed at the cemetery, and the burials were unattended except for workmen, a city official and two unidentified representatives of the Protecting Powers. The graves were not marked.

There were other versions too: some less bizarre, some considerably more so. One report, neatly bound and complete with photos of Kleiststrasse, Nollendorfplatz, the S-Bahn station, the U-Bahn station and a coloured street plan showing Moskvin's path in red broken line, had been assembled by the CIA office in Berlin, working in conjunction with its offices in Bonn and London. This revealed that Moskvin had been preparing material to incriminate falsely an unnamed US citizen resident in London. It concluded that the KGB were determined that Moskvin should not be taken alive and questioned by the British.

Bernard Samson was seen firing at Moskvin but his report, given verbally, said that his rounds all went wide. Some people have pointed out that the great preponderance of rounds that Samson has been known to fire, prior to this, hit his targets. Frank Harrington might have thrown some light on the subject, for Frank had been seen on the S-Bahn station brandishing a gun (something that stayed in the minds of those who saw him because Frank had never been seen with a pistol before, or since), but London Central never asked Frank for an account of it.

Bret Rensselaer was also there but Bret was never questioned specifically. He was hit and severely injured, and by the time he'd recovered sufficiently to contribute an account of it, the reports were complete and the incident had passed into Berlin's crowded history. The doctors at the Steglitz Clinic saved Rensselaer's life. He was in the operating theatre for three hours and went from there into an intensive-care ward. Next day his brother flew in on some specially assigned US Air Force jet that came complete with doctors and nurses. He took Bret back to America with him.