‘I thought about that all last night, Otto. I went over every minute of every contact I had with him, believe me. The first time we met was at a conference for military scientists and engineers in early July at Humboldt University. Afterwards there was a big reception, the kind where hundreds of people mingle together. We just got chatting and he asked me what I did. He said he’d be interested in talking to me in further detail about how to cope with machinery operating at very high temperatures; he said the Luftwaffe might want to know more. We had one meeting at a bar on Unter den Linden, which was when I told him about your company and the high quality of your parts. He said he’d like to meet you when you were next here, which is how that dinner in August came about. I’d told him when you were going to be here, and he said he’d be in touch. Two days before you arrived, he bumped into me in the street and we agreed to meet at the restaurant. He never phoned me, and I can’t imagine there’d be anything in writing.’

‘But we don’t know for sure that he’s not been captured, do we? He could still be alive.’

They left the factory at two o’clock. The car was to take them back to the hotel to collect their cases and then on to Tempelhof. As they pulled out of the factory, Otto slumped in his seat, mopping his brow. ‘I’m never coming back here again, never. When I get back to Copenhagen – if I get back to Copenhagen – I’m going to tell my boss I’ve had enough of travelling. I have no intention of ever leaving Denmark again; in fact, the way I feel now, I never want to leave my apartment again. If he doesn’t let me give it up, I’ll resign.’

‘Won’t that draw attention, though?’

Otto turned to Prince, a slightly manic look on his face. ‘I don’t care, Peter, I really don’t care. I’m never coming back here again, ever.’

They both knew that if there was the slightest hint of suspicion over them, they’d be stopped at the airport, but it was an incident-free departure, though not without the inevitable tension.

Their papers were fine, their visas were checked, their cases gone over and Otto was able to satisfy the Gestapo officers that the purpose of their visit had been to help the Reich. Their flight was at five past six, and they entered the departure lounge an hour before that. Otto went to the bar to buy them each a beer and came back with a copy of Der Angriff, the Nazis’ afternoon newspaper. Its front page was dominated by a head-and-shoulders photo of Kurt, under a stark headline: Luftwaffe officer killed in Mitte shooting.