Rebecca felt him take her weight.

Here goes, she thought.

She rolled over the gutter and slid into thin air.

The rope pulled painfully around her chest, above her breasts. She dangled in the air for a moment, then Bernd played out the rope and she began to descend in short jerks.

They had practised this at her parents’ house. Bernd had let her down from the highest window all the way to the backyard. It hurt his hands, he said, but he could do it, if he had good gloves. All the same, she was instructed to pause briefly any time she could rest her weight on a window surround to give him a moment’s respite.

She heard shouts of encouragement, and guessed that a crowd had now gathered down on Bernauer Strasse, on the west side of the Wall.

Below her she could see the pavement and the barbed wire that ran along the façade of the building. Was she in West Berlin yet? The frontier police would shoot anyone on the east side, but they had strict instructions not to fire into the West, for the Soviets did not want any diplomatic incidents. But she was dangling immediately above the barbed wire, neither in one country nor the other.

She heard another burst of machine-gun fire. Where were the cops, and who were they shooting at? She guessed they would try to get up on the roof and shoot her and Bernd before it was too late. If they followed the same laborious route as their quarry they would not catch up in time. But they could probably save time by entering the building and simply running up the stairs.

She was almost there. Her feet touched the barbed wire. She pushed away from the building, but her legs did not quite clear the wire. She felt the barbs rip her trousers and tear her skin painfully. Then a crowd gathered around and helped her, taking her weight, disentangling her from the barbed wire, unwinding the rope around her chest, and setting her on the ground.

As soon as she was steady on her feet, she looked up. Bernd was on the edge of the roof, loosening the rope around his chest. She stepped backward across the road so that she could see better. The policemen had not yet reached the roof.

Bernd got the rope firmly in both hands, then stepped backward off the roof. He rappelled slowly down the wall, slipping the rope through his hands as he went. This was extremely difficult, because all his weight was supported by his grip on the rope. He had practised at home, walking down the back wall of the town house at night when he would not be seen. But this building was taller.

The crowd in the street cheered him.

Then a cop appeared on the roof.

Bernd came down faster, risking his grip on the rope for more speed.

Someone shouted: “Get a blanket!”

Rebecca knew there was not enough time for that.