His face had been bloodless. ‘He told me he’d just come back from the inauguration of a new installation at Sachsenhausen, one identical to installations that have been in operation for months past in the camps in Poland.’ With shaking hands he had poured himself a large brandy. ‘It’s called “Station Z” and it enables large numbers of prisoners to be gassed all at the same time. Huge numbers. He told me as if it were something I must already be aware of. As if it were quite common knowledge.’

He had drained the brandy in a huge gulp and then, unsteadily, he had said, ‘I have to work out a plan, Hester. A plan whereby none of the prisoners working for me ever go back to Sachsenhausen. And I have to work out a plan whereby I can have more workers allotted to me, because that’s the only way they are going to survive.’

He had succeeded in both his aims. Whenever mention was made of any of his original workers being returned to Sachsenhausen he insisted that as they had all now become highly trained, he couldn’t lose them without production levels plummeting.

And he had negotiated that large numbers of slave labourers be allocated to the House of Remer steelworks in the Ruhr. As at Spandau, the arrangement he negotiated with the Concentration Camp Section of the SS Main Administrative and Economic Office was that for efficiency’s sake there would be no daily transporting of slave labourers backwards and forwards from the camp they were presently imprisoned in, but that at his own expense he would establish a Forced Labour Camp within the steelworks perimeter. In that way, he had argued, the labour of those assigned to him could be more fully exploited.

Grudgingly, permission had been given. It was a camp whose fenced perimeter was still patrolled by SS guards—there had been no escaping that condition—but no guards oversaw the prisoners as they worked. There were no opportunities for casual beatings and no fear of starvation or torture. As at Spandau, his workers had the benefit of shower blocks and a laundry, his argument for them being that an outbreak of typhus would set essential war production back by weeks.

There were now three hundred women slave labourers in the haven of the Spandau factory and eight hundred men at the Ruhr steelworks and both she and Claus knew they would all count against him when the war was lost and the Allies began their tally of war criminals. As an industrialist producing steel and armaments he would be on the list as a matter of course, but as a user of slave labour his name would be asterisked in just the same way as the names of those industrialists who had worked slave labourers to death in their thousands.

As the air raid took place above her, shaking the walls of the cellar, Hester felt sick at the thought of what would then happen to Claus. The most optimistic scenario was that he would be imprisoned. The worst, that he would be executed. If he were to be executed, she knew it was something she would never, ever, be able to come to terms with. Not only because she knew how unjustified it would be, when his reason for demanding as many slave labourers as possible was in order that he could save their lives, but because, next to Hugo, he had become the dearest person in the world to her.