‘Where do you think the Kestrel Line goes from here?’ Hanne had calmed down and the atmosphere in the room had changed. It was clear they were now on the same side.

‘Look…’ Jožef pulled a map from his pocket. ‘We’re here, just south of Villach. The Nazis chose this place well: we’re only five miles or so from the Slovenian border, but more importantly from their point of view, maybe seven miles from Italy. My guess is that the Kestrel Line ends there.’

‘Across the Gailtal Alps,’ said Edvard, ‘the natural habitat of the kestrel.’

Prince left Vienna as dawn broke over the city, a muted light filtering through the black clouds as the sun rose from the east. The rain was so heavy it felt as if the waters of the Danube had been whipped up and were being sprayed over the southern suburbs as the Red Army staff car picked its way through the bomb-damaged roads. Gurevich sat in the back with Prince, toying with an unlit cigar and wiping the condensation from the window with a leather-gloved hand.

‘It still looks like a battlefield, doesn’t it, my friend? I’m told the campaign to take the city was particularly bitter – our offensive was mostly from the south, round here. It would explain why the place looks like Berlin. I almost feel at home!’

They picked up the pace as they drove through Wiener Neustadt, continuing south through the Soviet zone. Just after the small town of Friedberg, the car turned off the road, driving along a narrow track through a wood and pulling into a small clearing, where it parked alongside an unmarked black Daimler. Iosif Gurevich told his driver to leave the car and turned to look at Prince.

‘I do what I can to help you, I hope you understand that. I feel an obligation to you – we are friends, I can trust you.’

Prince said he was very grateful, but the Russian hadn’t finished. ‘I’m not naïve; I’m a Red Army officer – a commissar. I know that politics matters and dictates the relationship between our countries, and of course my loyalty will always be to the Soviet Union. But I see no reason not to help you as a friend when I can – when our interests happily coincide. I don’t know if we’ll ever see each other again: I will return to Berlin, but my future may be uncertain. I just want you to know that you can trust me, and all I ask is that maybe one day you will ask after me.’

‘Of course, I—’

‘But use your discretion, please – it may not look good if people know I have a British friend!’

They embraced, and Gurevich told Prince the other car would drive him to Klagenfurt; he’d better get a move on.

Just before noon, the Daimler stopped in a side street in the centre of Klagenfurt. The driver – a heavily built man with notably thick eyebrows and bloodshot eyes – turned round and spoke for the first time, in a deep voice: walk along this block, take the first left and then turn right – the building you want will be ahead of you. You’ll spot your flag.