‘Because the commander was crazy about chess. He was a grandmaster who played at all the big tournaments in Europe. He found out I was the Youth Champion. He wanted to play me. I did not want to, but they threatened to torture my father more if I didn’t. The Stasi took me to his office. It had huge wooden doors that opened into a room that was as big as your hall at school. It had just one desk in it – the commander’s desk with a chessboard set out on it. And he was standing behind the desk, waiting for me in his uniform, many medals on his chest. He told me to sit down and play, even though I knew you do not play games with the enemy. But when your father is being tortured in a room only metres away, you will do anything. I made the mistake of beating him. I thought he wouldn’t want to play any more, but instead it made him want to play me more. He made me teach him moves in exchange for not sending my father to another camp far way, near Poland.’

‘But he was a commander,’ I say. ‘He couldn’t play chess all day.’

‘But he could,’ says Granddad, ‘that is the point. In East Germany, if you were a good athlete – a runner, a swimmer – or if you were good at anything at all, the government would help you. And because of their mental strength, chess players were treated like kings. So of course I played the commander, to help my father. We played every day, sometimes twice, and he took me with him to play tournaments in the East with the Russians. I was not allowed to play, I was just there to help him prepare before every game and replay them after. I taught him every attack I knew, invented new ones and taught him those too, and he won every tournament in the East. I thought I’d fulfilled my side of the bargain, that maybe instead of threatening to send my father to Poland he would let us all go. He said he would, but only if I helped him win the World Chess Championship in 1962, that was being played in West Berlin.’

‘The other side of the Wall?’