Knudsen raised his eyebrows and pursed his mouth, as if to help him find the right response. ‘I’ll answer you in a very Danish way, Peter, by asking you a question: why would I not do this? It is my duty. I’m not a political man, though I’ve always been a supporter of the social democrats. For me, like most Danes, having the Germans occupy our country is an anathema, a terrible thing. But compared with the rest of occupied Europe, we don’t suffer much. What angers me most is what the Nazis are up to elsewhere in Europe. They must be defeated and I swore to myself that if I found I was in a position whereby I could assist the British, I would have no hesitation in doing so. I rationalised it like this: I wouldn’t go out of my way to find out something, but if something found me, so to speak, I would not ignore it. And that is what happened with Kurt, the Luftwaffe officer. He told me things I knew would be of interest to the British. And here we are! I’ve been divorced for many years and I have no close family. I’ve lived a good life, a very comfortable one. It would not be the end of the world if it was sacrificed for a greater cause. I hope that doesn’t sound too sanctimonious, but you did ask me.’

‘But your contact, how did he know to put you in touch with Kurt?’

‘That’s a good question, Peter. Maybe by the time we return we’ll know the answer to it. Look, we’d better move. Not too fast, though; let’s make sure we’re at the end of the queue. That way they’ll be in a hurry by the time they get to us.’

‘Date of birth?’

The Gestapo officer was a good two or three inches taller than Prince and appeared to be standing on a small platform behind his desk. He towered over the passengers in the queue.

‘Eighth of July 1901.’

‘Birthplace?’ Given the circumstances, he didn’t sound especially unpleasant.

‘Helsingør.’

‘Occupation?’

‘I’m a ship worker.’

‘Why is a ship worker flying to Berlin?’ A bit more unpleasant now, a hint of a sneer.

‘I’m actually a maritime engineer: my company is doing some work at a locomotive manufacturing plant in Berlin and my expertise is the operation of large boilers – industrial ones: the type you get on ships and trains.’ Prince could feel his stomach tightening. The Gestapo officer looked just like the kind of person who spent his leisure time looking at boilers, the industrial variety.

‘Your age?’

This is when they get serious; when they mix up the questions, go back on ones they’ve asked before but in slightly different ways.