He waited while Prince poured a large glassful. ‘I do worry that when we train our agents, we cram their heads full of information and it’s sometimes hard to see the wood for the trees. I always try and send them off with a short summary of what the mission is about so they can be clear as to what I expect.’

He stood up and circled the dining table before sitting down next to Prince.

‘The tide of the war has turned in our favour, no question about that. But we mustn’t be complacent; there’s still an enormous amount of fight in the Germans. They’re a formidable enemy and a clever one. The biggest threat to this country could well be from these long-range rockets they’re developing. They could cause us untold damage; they could even reverse our fortunes. I’m not suggesting they could cause us to lose the war on their own, but if the rumours are close to the truth, they could set us back months, quite possibly even a year or two. That would be a disaster. However, there’s a worrying degree of scepticism in some quarters. There are people in Whitehall – some of them quite influential – who insist these rockets pose no threat, or that the threat is exaggerated, and they’re trying to influence Winston accordingly.

‘Recently our head of station in Stockholm was approached by a Danish businessman, whom we call Agent Horatio. He travels to Berlin frequently for his work and claims that while there, he’s picked up something about the rockets. But there’s a limit to what we can do with him from a neutral country: I need my own man on the ground in Copenhagen to run him. First, though, you’ll need to check him out – we cannot even be sure we trust him. In the end, it may well be a matter for your judgement. If you think he passes the test, I want you to milk him for whatever intelligence he has.

‘I don’t think I’m exaggerating, Prince, when I say that this mission is of the utmost importance: if half of what we hear about these rockets is true and they extend the war by even a couple of months, that could be a disaster. And there’s something else: Denmark is also very well placed to gain information about the rockets. The Germans are developing the damn things at a place called Peenemünde, which is on the Baltic coast, very close to Denmark. They’re even test-firing some of them into Danish territory.

‘So that’s your job, Prince. Run Horatio, find out what you can about the rockets, supply me with the evidence I need to persuade the fools here that this is a genuine threat. Do that and you’ll be a hero.’