Wilde had visited Camp 020, and he knew that it was a harsh place. Captured German agents had been housed there during the war, and now it was used to confine various senior Nazis for prolonged interrogation. He knew that some of the techniques used there didn’t stop very short of torture: prisoners were bawled at, subjected to long periods of isolation in darkness or glaring light and given cold baths. Wilde had heard, too, of mock executions.

Now, here in the more pleasant suroundings of Grosvenor Street, he introduced himself. ‘I am Professor Thomas Wilde of Cambridge University but today I will be asking you a few questions on behalf of the Office of Strategic Services.’

The German struggled up from his chair and bowed briskly. ‘It is my pleasure to meet you.’

‘Likewise,’ Wilde said, though the word stuck in his craw. Whatever Schellenberg’s alleged efforts to broker a peace deal and save concentration camp inmates towards the end of the war, he had been right-hand man to Himmler. Nothing could excuse that. He turned to the Marine. ‘Wait outside if you would, soldier.’

‘Yes, sir.’ The Marine did a sharp about-turn, exited the room and closed the door behind him.

‘Now, Herr Schellenberg, sit down.’

‘Thank you, sir.’

They sat opposite each other. Wilde noticed that the room stank of sweat, the sort of smell you get in a sickbay when men are feverish. ‘Would you like water or a cup of tea?’

‘That would be kind, sir. Tea, if I may.’

‘I’ll have it fixed in a short while.’

‘You know, Professor, I have heard a great deal about you. You were famous at Prinz-Albrecht-Strasse. We had a thick file on you in our SD records. I recall you had made a deadly enemy of our Gestapo leader, Heinrich Müller. He discussed organising an effort to assassinate you.’

‘Well, that didn’t go too well, did it. What became of Herr Müller?’

Schellenberg shrugged and his thin, bow-shaped lips formed a half-smile which made him look unpleasantly self-satisfied. A film of sweat coated his broad brow. ‘I have no idea. Is that why you’re here – to find Müller?’

‘No. I want to find Adolf Hitler. Tell me, Herr Schellenberg, how do you like to be addressed these days? General or plain mister?’

‘I would like to be called Herr Doctor, if that suits you. I am a doctor of law and proud of my doctorate. I hope one day to enter academia if I am allowed. I am not so proud of having been an SS officer.’

‘Are you being treated well? If you don’t mind my saying so, you look rather ill. Have you been seen by doctors since you arrived in England?’

‘Oh yes, I have been seen by doctors. Apparently I am der hypochonder, you know – feigning sickness.’

‘Hypochondriac.’

‘Yes, that is the word. But you are correct – I am ill. I have had a severe gut problem for years, but it is worse now. So I hope you will excuse me if I need the lavatory in a hurry.’