‘What went right? We got greedy, we thought the war was all but over and started thinking about after, what would be our role, what would be the Folly’s, the order’s, England’s, the Empire’s.’

He looked at the bottle of water he held, as if trying to remember what it was for. ‘Hubris is what it was.’ He took another sip and when he spoke again his voice was stronger.

‘Nightingale was against it from the start, said we should send in the RAF and bomb the camp from altitude. He said it was the only way to be sure.’ He gave me a puzzled look. ‘Did I say something funny?’

‘No, sir,’ I said. ‘You mentioned being greedy. Greedy for what?’

‘There were some bright young sparks before the war,’ said Hugh. ‘On both sides. People like David Mellenby, who said they thought it might be possible to formulate a theory that would unite magic with relativity.’ Hugh paused again, eyes unfocused. ‘Or was it quantum theory? Which one is the one with the cat?’

‘Schrödinger’s cat?’

‘That’s the bugger,’ said Hugh.

‘Quantum theory,’ I said.

‘Closing the gap, he called it,’ said Hugh. ‘Had lots of foreign friends, particularly in Germany – all practitioners or boffins – which was damned unusual, you understand. He took the start of the war very badly, saw it as a personal betrayal. You see, the Nazis took his work and . . . I’m not sure what the word is.’

‘Perverted it?’

‘No,’ said Hugh. ‘We thought they might have closed the gap, but the methods they used . . .’ Hugh was trembling and I considered calling his daughter, but then I saw the look in his eyes and realised it was anger. Not just anger, but rage – even seventy years later. ‘They did terrible things to live prisoners, to men and women and the fae and . . .’

He stopped, his chest heaving, and looked around his study, blinking his eyes.

‘And, being German,’ he said finally, ‘they wrote it all down, typed it up in triplicate, cross-referenced it and filed it neatly in a hundred filing cabinets in a central bunker in a camp near a town called Ettersberg.’

‘Oh shit,’ I said. I realised the implications. Hugh gave me a reproachful look. ‘They wanted the research data,’ I said. ‘That’s what the operation was all about.’

‘We couldn’t let the Russians have it, or the Americans, or the French for that matter,’ he said. ‘It was obvious to everyone by ’45 that this was the Empire’s last hurrah. The Russians were gearing up to win the Great Game and the Yanks couldn’t wait to get us out of the Far East. I think some believed, including David, that this could put us back in the game.’

‘What game?’