But it is, he thought, it hurt. She was sharing this with him. Perhaps she still cared for him, enough to trust him with this?

‘What was he doing in the war?’

‘He was in the Wehrmacht, part of the occupying force in the Channel Islands.’ She smiled again. ‘He spent his war learning cricket in Sark. And English.’

John wondered if Anatoly had got it all wrong, that Betty Fisher was not Bette Fischer but some other namesake.

‘What’s his name?’

‘Arnold Fisher,’ she said. ‘He changed his name too. Anglicised it. It was Hermann Fischer.’

John stood behind her, watching her reflection in the glass. Her hair had been twisted into a pleat and a wisp had come loose, resting on her collar. He wanted to lift it, tuck it back in place, brush her neck, smell her scent.

‘There’s a physicist called Hermann Fischer. Is that your father?’

‘No. He’s an engineer,’ she said. ‘He works on aeroplanes. On engines.’

‘Where?’

‘At the de Havilland factory, in Hatfield. I told you this ages ago.’

‘Why did he leave Germany?’ John said.

‘He never went back,’ Betty said. ‘He was a POW. He fell in love with England, and England was crying out for workers at the end of the war. Europeans, ideally, like him.’ She laughed. ‘The people who came in the end were West Indians. But one or two of the POWs stayed, like my father.’

This was going nowhere. Anatoly had got the wrong man. Fischer was a common enough surname, and Hermann a popular first name. This whole business was shambolic, he thought, had cost him his love, his sanity.

‘So who is Hermann Fischer the physicist?’ Betty said, daring him to contradict her.

John took a deep breath. He looked at her, trying to lock her eyes with his, pumping up his courage.

‘There’s a man by that name who works for de Havilland,’ he said. He spoke slowly, softly. ‘In a secret division of the company. He was a German physicist during the war. Among other things, he helped develop the V1 and V2 rockets.’

She faced him, her colour fading from her cheeks. ‘Go on.’

‘After the war, he was invited to come to Britain.’ His eyes steadied on her, monitoring her, drilling into her, willing her to respond. ‘A number of Germany’s top scientists left at that time. Some went to the Soviet Union. Some to the United States. Some here.’

‘So?’ she said, shrugging her shoulders, a tone of defiance. ‘Why? What’s that to do with my father? That’s some other man.’

‘They came,’ he said, his voice level, authoritative, ‘to work on the nuclear programme.’

Betty opened her mouth, hand to her lips. ‘I didn’t know this,’ she said. ‘Those scientists? Who worked for the Nazis? Came here?’

He nodded.