‘A bit quicker than that, though – just normal speed, that’s it. If we’re stopped, tell them we’ve been looking for a restaurant and walked up to Unter den Linden but decided to return to the hotel instead. Tell them we’re Danish businessmen and I don’t speak a word of German. Act confused as to why we’ve been stopped, but don’t be rude.’

They paused at the junction with Kommandantenstrasse. As they looked up and down it, they could just make out the figure of Bruno, walking faster than Prince would have liked, though he was at least heading away from the restaurant rather than back towards it.

No sooner had they crossed Kommandantenstrasse than they heard the sound of a car speeding towards them from behind and screeching to a halt.

‘Oh my God,’ said Otto.

‘Be calm. Remember what I told you to say.’

A long black Mercedes sedan had pulled alongside them, its front wheels mounting the kerb in case they were disinclined to stop. Three men, clearly Gestapo, climbed out.

‘Halt: stand still and keep your hands by your sides. When I tell you, give us your papers, but do so slowly.’

Prince glanced at Otto.

‘Don’t look at each other! You – move away from him, over here! Don’t you hear what I’m saying?’

‘My colleague does not understand or speak German, I’m afraid.’

‘I don’t care. Papers.’

They each handed their papers over to a different officer, who studied them for a while and then consulted the man behind them. As he moved forward, Prince realised he recognised him: it was the shabbily dressed man who’d wished them good afternoon in the Tiergarten the previous afternoon.

He spoke with a sharp working-class Berlin accent. ‘Where have you been?’

Otto cleared his throat and shifted anxiously from foot to foot. ‘You can see from our papers that we are staying at the Excelsior on Askanischer Platz. We decided to see if we could find a restaurant to eat at tonight because we fancied a walk too, and the concierge kindly gave us passes. We went up Friedrichstrasse to Unter den Linden but couldn’t see anything we liked or that had a table, so we decided we may as well eat at the hotel after all. That’s where we’re heading now.’

‘Why have you come this way? You’ve gone round in a circle: why didn’t you go down Friedrichstrasse or Wilhelm Strasse or even Jerusalemer Strasse?’

‘You’ll have to excuse us, sir, but we’re guests in your city. We are not terribly familiar with it, and with it being so dark… I’m afraid we must have become disorientated.’

‘Enough. You come over here with me.’ It was one of the other Gestapo men, gesturing for Prince to join him a bit further down the pavement, away from Otto.

‘But my colleague doesn’t speak German!’