By the time the train arrived in Greifswald at a quarter past five, he’d drunk the best part of Frau Henlein’s bottle of schnapps. He wouldn’t say he was beyond caring, or even that his guard was down, but he was certainly more relaxed than he ought to have been in the circumstances. He insisted on carrying her cases to the ticket barrier – where he was waved through – and was introduced to her daughter.

‘He’s such a nice man – but so unwell!’

Greifswald station was small: just two platforms as far as he could make out, and a large number of troops lined up along one of them. He bid farewell to his travelling companion, more grateful for her company than she’d ever realise, then followed the other passengers out of the station onto the Bahnhofstrasse. He paused to tie his shoelaces, which he’d been advised not to do (too obvious, old chap), and set off along the road.

By the time he saw her and recognised her, she’d already embraced him.

‘You look so well after such a long journey!’

It was the woman from Berlin: the woman with the distinctive hats. She was wearing the turban-style one now and she looked genuinely pleased to see him.

‘But I could do with a good meal and a proper sleep.’

She nodded. All was in order. ‘It’s good to see you, though you actually look terrible. I have a car just along here, and some papers for you. You’re my cousin from Dortmund, by the way.’

‘You’d better tell me your name.’

‘Of course. I’m Sophia. Sophia von Naundorf.’

Agent Blackbird – Sophia von Naundorf – had rented a small villa on the outskirts of the town overlooking the mouth of the River Ryck. It was in an ideal location: set at the end of a single-track road, the closest neighbours the other side of a field and the villa itself surrounded by a high wall, with an iron gate of similar height separating the drive from the road.

The house and the area around it were bathed in darkness, the moon blurred by clouds. She led Prince into the villa and he waited in the hall while she turned on the lights.

‘They take the blackout very seriously around here: the British don’t seem to know much about the area, but it’s near Rostock so there’s always a danger they could hit the town. You look like you could do with a bath. I’ve laid some things out for you in that bedroom. When you’re ready, I’ll make you a meal, then we can talk.’

It was an incongruous setting for their first proper meeting. They sat opposite each other in a small but elegant dining room, the French-polished table replete with what Sophia apologetically described as a modest meal.