Too young to remember much before 1986 when Anatomie was barnstorming around Czechoslovakia, and still at the stage when he was unsure of how to assess the immediate past, Eduard looked baffled. ‘If you don’t mind, I’ll head for the nearest bar.’

A little later the taxi dropped Petr in Oderberger Strasse, close to the entrance of Mauerpark which had marked the former boundary between East and West. It was a rundown, seedy area with graffiti scrawled over the buildings and dismal street lighting.

Laure was waiting for them flanked by several women, plus a tall, square-faced man in a Loden coat and a baseball hat. The women were Embassy wives and the man was their German guide.

It was bitter weather made worse by the wind, and the group had dressed for the cold in heavy overcoats and hats. Petr judged that Laure’s serviceable grey coat had been chosen to suggest a lowly embassy status which may, or may not have been, near the mark. He had not made up his mind on that point. With it she wore a black beret (which looked French) pulled down over her ears. Apart from a polite greeting, she paid no special attention to Petr. As they moved around, he observed her masterminding the group with a calm, assured competence, a definitive marker between the older Laure and the younger one.

The group was led into an anti-tank defence building which, explained their guide, had been abandoned after the end of the war. ‘This made it a perfect place to dig.’ He shepherded them over to an opening in the concrete floor. Here a shaft had been driven into the earth and reinforced with crude wooden posts. ‘It was discovered some weeks ago when engineers working on new underground water storage systems cut across it. It’s known as Tunnel 15 as, it has been established, fifteen people managed to get out through it before it was shut down.’

The shaft was approximately five metres deep. Dutifully, the group peered down into it. Petr glanced around at the rapt faces. Did he sense a superiority in the attitude of the British clustered around the shaft? An inner monologue that ran along the lines: we would never allow a society where people felt they had to dig to escape?

But what, he reflected grimly, did the class-ridden British know?

He went to stand beside Laure. She shot him a look that told him nothing.

Their guide continued, ‘Tunnel 15 runs for about eighty metres and comes up in a disused outside lavatory behind a block of flats. There are several stories about the escapers, some of them fanciful. It’s estimated that many more people planned to go through, but they were betrayed. The shaft in the East was sealed off by the authorities.’

The British women murmured among themselves.