‘I’m sorry about your mother. And your grandmother.’ She turned her face out of the wind. ‘Let me see. Is it the profound feeling of brotherhood that says that you must spy on everyone from morning to night? Or the upholding of equality that says only Party officials have telephones that work and get to shop in the Tuzex stores where Joe Public is banned? Or is it the fervour with which the workers perform even the most menial tasks because they believe in the general good. Or is it that they’re frightened witless?’

She was speaking so softly that only Petr could hear.

The guide was in full flow. ‘The story goes that, of the fifteen people who got through, five were from the same family, the Webers. The Stasi were clever in working out who were engaged in anti-Party behaviour.’ He paused for effect. ‘For instance, listening to, or watching, the BBC was forbidden. Of course, they couldn’t patrol the airwaves so officials would visit kindergartens and ask the children to draw their favourite television character. Little Joel Weber was anxious to obey and drew a beautiful picture of the BBC’s Bill and Ben, the Flowerpot Men. That was that. The family had only had a few hours to get out. The story goes that when Grandmother Weber arrived there was concern she was too stout to get through until she revealed that she had wrapped her cat up in a bag and tied it around her middle. But get through she did, dragging the cat behind her.’

Laure asked Petr, ‘Does it ever worry you that you’ve survived, and very well, and others did not?’

He bent down and picked up a stone. Rounded and very dark in colour, its hunched shape was reminiscent of a beetle. Flipping it from one hand to another, he said. ‘You have to be careful, Laure, about these things. Don’t go blundering in.’

The guide rounded off the session. He waved his arm in the direction of the building. ‘After the discovery of this tunnel and others, it became increasingly dangerous to build tunnels and dissidents trying to get out resorted to alternative methods. Some made it to Prague and got out that way. Others to Budapest.’

He felt, rather than heard, the name on Laure’s lips. Tomas.

Tomas could be added to the phantoms who lived with them: the eternal dissident, the eternal escapee. If he had been an East Berliner, Petr had no doubts that Tomas would have crawled along a rank and narrow tunnel, with earth clogging his nostrils. As a Czech, he had had to choose other methods.

The group were thanking the guide and Petr took the opportunity to tell Laure, ‘I’m leaving at the weekend.’

‘Which day?’

‘Sunday afternoon.’