He and Otto met in reception at seven o’clock. His colleague had already had breakfast and looked as if he’d slept well. He was sitting on a chair reading Völkischer Beobachter, which he folded up as soon as Prince arrived, though not before Prince spotted the words ‘Heroes’ and ‘Stalingrad’ on the front page.

As they walked towards the entrance, a woman swept past them, her long coat brushing Prince and the scent of a powerful perfume following in her wake. As she turned to say something to a porter, he realised it was the same woman he’d seen the previous afternoon: the gentle accent, the remarkable eyes. This time she was wearing a fawn bonnet-style hat with a wide dark ribbon round it, tied into a large bow at the back. For a brief moment she glanced at Prince. It was not a look of recognition or communication, nothing like that. But she was clearly looking at him rather than his companion. Then she turned again, said something to the porter and disappeared down the steps.

Bruno Bergmann had sent a car to collect them: the journey across the city took forty minutes. They were stopped at two checkpoints, there was another delay when they were halted for a military convoy to pass, and Prince noticed that at least two roads on their route were closed due to what appeared to be bomb damage.

Otto leaned over, the coffee warm on his breath. ‘Before the war, this journey would take twenty minutes!’

The Spandau Locomotive Engineering works were vast, taking up three blocks in an area that seemed to be an uncomfortable mix of industrial and residential. Bruno Bergmann was much as Otto had described him: not unfriendly, but no small talk, and very much the engineer. He wore a stained light brown work coat over a shirt and tie.

The first hour was taken up with a tour of the factory, with Otto translating everything from German into Danish for Prince’s benefit. Then it was up an iron ladder attached to the wall onto a large gantry overlooking the main assembly plant.

‘What did you think of the factory, Herr Rasmussen?’ Bruno asked.

‘Very impressive; every bit as impressive as Otto said it would be.’

‘You’re a maritime engineer then? I am sure we have much to learn from our seafaring colleagues!’

Worried that he was about to be asked technical questions, Prince replied hurriedly, ‘That was some time ago, I’m afraid. Now I’m as rusty as some of the old boilers I worked on. I—’