‘February nineteenth,’ he said. ‘Same as mine. Same birthday. Same year. That’s what broke the ice. And then she danced.’ He looked up. ‘A polka. Can you believe that? It was a joyous moment.’

Lieselotte had looked happy, for one second, that last night, before she went to see him again. Betty had no doubt that John was the soldier she had planned to meet.

‘We forgot where we were, who we were. Why both of us were there.’

‘And then?’

‘Then we agreed to see each other again, and she suggested the Lichtensteinbrücke. She said it would be quiet, and we might be able to walk along the Landwehr canal.’

He was cradling his cup, but his hand trembled. She let him steady himself.

‘Only she didn’t come. Instead, two Russians were there, and they took me to her.’ He put his hand over his eyes, dragged it over his face. ‘She’d been murdered.’ His voice grew soft, quavered. ‘Raped, murdered.’

Betty stood up and walked over to the window, staring into the chasm of the street below, the blackened buildings, the sombre porticos of the British Museum. She wanted to howl like an animal, rip out her heart and every ounce of feeling she possessed, rid herself of the agony of knowing.

‘You see,’ John was saying, ‘it may have been an ambush. It was an odd place to meet. It was isolated, out of bounds, almost. Perhaps I had been lured there—’

A dam broke within her. She spun round, flew at him, hammering her fists into his shoulders, his body.

‘She was my sister.’ Her voice was loud, choked with sobs. ‘She was my sister.’

He sat back in his chair, hands up to protect his face. ‘What? Your sister?’

‘This was no ambush. She’d never lure you there. That’s not who she was. She hated the Russians, after what they did to her.’

‘I didn’t know that, Betty,’ he said. His voice had a catch in it and she watched as he struggled with his words, small beads of sweat glistening on his forehead. He looked at her, examining her face, her eyes and nose and mouth. ‘How is that possible?’ He breathed out, pulled his handkerchief from his pocket, wiped his forehead. ‘I’m so sorry. If I’d known she was your sister I’d have broken the news more gently.’ He stiffened in his chair, holding out a hand towards her. She looked at his hand, at his frame sunken in misery. She felt a sudden rush of tenderness towards him, an urge to touch his hand, hold it, squeeze out all this sorrow. His fingers flexed. She waited until he withdrew it.

‘I couldn’t be sure, at the time,’ he was saying. ‘That it wasn’t a set-up.’