‘There were bodyguards everywhere,’ Granddad continues. ‘Even if I’d tried to escape like my father wanted, I couldn’t have, because they followed the commander and me everywhere we went, to every game. For three days, I helped the commander prepare in the mornings, playing chess in his room, and even in our heads as we went down in the lifts to the main hall. He won his first four matches and was in the semi-final against a military general from Russia. They had never played each other before and the commander was very nervous. He demanded I tell him my best moves, something no other player would know. If I helped him reach the final, he wouldn’t just not send my father away, he would release him and remove my mother’s house arrest the next day. That evening was when I taught him my best move. That’s when I taught him . . .’

‘The Spreeborgen Variation,’ I say slowly.

‘Yes.’ Granddad nods. ‘You see, Felix, the Yugoslav Attack wasn’t his, it was mine. And he used it the next morning to beat the Russian general. Afterwards we went back to his room. The commander was happy. Everyone was drinking and celebrating, even the bodyguards. That was when I asked him to keep his side of the bargain. I’d helped him to the final; now he had to release my parents. But he looked at me like I was talking backwards. “I have to win the final first,” he said.’

‘That’s not fair,’ I say.

‘No,’ says Granddad. ‘It was not fair and that night I lay awake thinking. Even if I helped the commander win, there would always be something else that stopped him releasing my parents – another game, another championship. He couldn’t be trusted. I wanted to call my father and tell him what had happened, but even if the Stasi allowed him to talk, I knew they would be listening.