‘Tell me I’m wrong, Herr Doktor.’

Todt was silent.

Wilde continued. All this information had been drummed into him during an intensive two-day course at an Edwardian manor house in the home counties north of London, following his week with Mrs Kemp in Cambridgeshire.

‘And if I’m right? Well, at a guess, you must understand the implications better than anyone in the Third Reich.’

‘You have come halfway around the world to spout propaganda at me, have you, Herr Esser? I thought you had something to sell. If you are not going to send tankers across the Atlantic, perhaps you have a new method of producing synthetic fuel, something we haven’t already devised for ourselves? Surely not wood-gas generators – we have that old technology.’

Todt must have known that wasn’t what he was offering; he was a details man, after all, and the wires from New York to Berlin had been specific in what was on offer, if not the actual science.

‘Synthetic fuel is a fine idea,’ Wilde said. ‘But surely you know the true reason for my visit.’

Todt smiled affably. ‘I receive few Americans. In fact, I believe you must be the first since . . . what, 1938 or 1939. Messages get lost in transmission. Yes, we both know what you are offering – improved fuel consumption. But you must also know that this is something we are already working on.’

Wilde knew, from his briefings, that oil – or lack of it – was the great problem facing the Nazi regime. Their reserves amounted to no more than a million tons, a tenth of that held by the British. And, stretched to the limit in the supply line through Russia, the German situation would soon become desperate if total victory was not achieved imminently. Germany needed a knockout blow, or a swift infusion of raw materials, the most pressing of which was oil.

It was hard to imagine warming to a Nazi, but on the surface, at least, Todt seemed genial and engaging. But who knew what lay beneath? He was no doubt efficient and single-minded. You had to be those things to have achieved what he had. But did that make him ruthless? Wilde really didn’t want to find out.

‘So you’re working on it. In which case, why did you agree to my visit?’ Wilde asked.

‘I am a man with an open mind. All innovations interest me. But you have to prove to me that you are worth dealing with.’

‘That is not easy. I am not just going to give you my technology. We need to meet on neutral territory where I can demonstrate what I am offering without revealing the method until a deal is struck and money – gold – paid up front, deposited in a neutral country.’

‘You do not trust me?’

‘I am a businessman and you’re engaged in a war. A gentleman’s handshake will not suffice in such circumstances. Look, what do your motorcycles average – maybe forty-five to fifty-five miles to the gallon in clear conditions on open roads? A lot less on difficult terrain and in poor weather. Well I can improve that dramatically – ninety miles to the gallon. And that’s a conservative estimate.’