At one stage Hanne wound down the window, but she soon put it back up: the smell was overpowering. Each time the car stopped, people would gather around it, the frightened eyes of emaciated children gazing at them as they pleaded for food. At one point a boy reached up to tap on the glass, and for a moment Prince thought it was his son Henry.

‘They did this to themselves,’ said the commissar, indicating a group of people fighting over something in a gutter. ‘Save your sympathy for their victims.’

‘I don’t have any sympathy for them,’ said Hanne.

‘Not even for the children?’

She shrugged and took her husband’s hand.

Gurevich pointed ahead of them to an enormous complex rising to their left high above the ruined landscape: Hohenschönhausen. Their progress was halted by a cart being pulled along the road in front of them. The driver sounded his horn, but it didn’t move out of the way. Gurevich said something to him in Russian and he edged forward, knocking the cart over. The two old ladies who’d been pulling it stood with their heads bowed as the car drove on.

Inside the prison they were directed to one of the few brick buildings and escorted to an upper-floor office where two uniformed men were nervously waiting for them. There was a long conversation, the two men seeming to defer to Gurevich, who eventually spoke in German to Hanne and Prince, gesturing at the men.

Comrade Orlov was the governor in charge of Hohenschönhausen, he said. Orlov looked old and tired, his head completely bald and his eyes red as if through lack of sleep.

‘And this is Comrade Kiselyov; he is in charge of the block where Schweitzer is held. Comrade Kiselyov speaks German. Maybe if we all sit down, he can tell us about the prisoner. I’ve told him you need information from him about a German fugitive.’

Kiselyov’s hands trembled as he spoke, all the time looking at a sheet of paper on the desk in front of him. His voice was surprisingly high-pitched.

‘Prisoner Schweitzer was arrested in May in Colmar in France, formerly an annexed zone of the Nazi Reich. He was arrested by a unit of French communists and eventually handed over to the Soviet Union. Under the special wartime provisions of section 117, subsection 48 of the Penal Code, he was eligible to be tried in Germany as someone who committed war crimes on German territory during the war against fascism.’

He paused to cough and gratefully sipped from a glass of water the governor passed to him. He glanced anxiously at the commissar to check all was in order before continuing.

‘The specific charges against Prisoner Schweitzer are that in the period from June 1940 to June 1944 he was an active agent of the Nazi Gestapo organisation, in which capacity he assisted the Nazis in carrying out war crimes and conducted war crimes himself, specifically but not exclusively a vendetta against members of the Communist Party of France and their relatives and associates. In terms of—’