‘When you’ve finished the map of the camp, put it in this.’ She handed him a black waterproof pouch. ‘Then bury it under the shale directly behind the post. When you’ve done that, scratch a mark underneath the life belt using a piece of shale. You know the Russian cross? That’s the sign you should use. I’ll look out for it and know to search for the pouch. Wait here, the group is coming closer.’

She returned a few minutes later. ‘They think I’m mad, but I’ve given them sausages and cigarettes. I don’t think they’ve ever heard of anyone wanting to break into a camp.’

‘Nor have I.’

‘They’re all wearing dark grey, so you’ll fit in. Quick now, good luck.’

It had been as easy as that. Prince had rolled out of the back of the Mercedes-Benz and scrambled over to the beach, where a group of bemused Frenchmen were standing as if they were looking at a ghost. As far as he could tell, there were around half a dozen guards on the beach, scattered around and mostly with their backs to the group. The two closest to them were huddled together, trying to light cigarettes. Summoning his best French, Prince wished the Frenchmen a good afternoon and said he’d like to come with them into the camp. Would they be able to help?

They gathered around him so he was now enclosed in the centre of their group. He suspected it was because they distrusted him rather than for protection. An older man moved close to him.

‘Where are you from?’

He’d known he’d be asked this and had decided he had no option other than to tell the truth. It was a risk he had to take. ‘I’m English. I’m here to find out about the camp.’

All the men looked at him through narrowed eyes. Despite the wind howling across the beach, he could hear the breathing of every one of them, and his own heartbeat. After what seemed like an eternity, the older man spoke, nodding his head approvingly as he did so.

‘Very well, we’ll help you, Mister Churchill. Stay in the middle of us.’ Then, in French: ‘Jean-Claude, give our friend your hat; Alain, swap jackets with him. It won’t do if he walks into Peenemünde looking like Mister Churchill, eh?’

They went back to repairing the sea defences, and after a while, the guards called them: they were to return to the camp. The older man walked close to Prince. He introduced himself as Émile.