‘Very well then – it’s not the way I’d have chosen to do it, but there we are. I’ve already checked out Agent Horatio and I’m as sure as I can be that he’s genuine. He’s a businessman called Otto Knudsen, fifty-three years of age, lives on his own in a smart apartment block in Gammelholm, overlooking the Nyhavn canal in the centre of the city. He doesn’t have a criminal record and because of this we don’t have too much on him, but thanks to the Gestapo, we have records of political affiliations in the 1930s at our headquarters, and certainly at the time of the general election in 1935, he was registered as a supporter of the social democrats. I was also able to check the municipal records, which show he was divorced many years ago and has no children. He works for a specialist engineering company based in Copenhagen called Mortensen Machinery Parts. He’s a salesman, and this job takes him to the other Scandinavian countries and into Germany. He therefore had good reason to be in Berlin and an excuse to be in Stockholm, where he contacted the intelligence people at the embassy. Stockholm gave us the dates he told them he was last in Berlin – the trip where he claims to have found out about the rockets. He told them he flew there. I have a friend who works at Kastrup airport; we were at police college together. I’ve told her I’m working on a sensitive case and she’s promised to let me see the passenger lists covering that period.’

‘And then?’

‘Is that the time? I need to get a move on, I really do. I need to be in the office at half eight. If it turns out Otto Knudsen did fly to and from Berlin when he says he did, I have one more check to make on him. If he still looks trustworthy after that, then you can approach him. Hopefully in three days we should know one way or the other. Until then, you stay here.’

It was six in the evening by the time Vicepolitiinspektor Hanne Jakobsen arrived at Kastrup airport on Amager island, south of the city centre. There’d been no flights for a few hours, but the small police station next to the terminal building was still open. Her friend Margrethe was the officer in charge; she’d sent one of the other three officers on duty for a meal break and told the other two to check the terminal building. She led Hanne into her office.

‘You have half an hour, Hanne, no more than that, though it’s extremely rare for the Germans to come in here. There are plenty around when there are flights, and they patrol the runway and perimeter, of course, but it’s best to be quick in any event. You asked for all of August, right?’

‘Yes.’