‘Umm, I see.’ Granddad studies the moves. ‘Pawn to e4. Pawn to e5. Knight to f3 . . . c6 . . . Bishop to b . . . But look, you are playing it too.’

‘I don’t think so, Granddad. I really don’t know what I was doing.’

‘Then you were being intuitive.’

‘Was I?’

‘Yes, like it comes naturally to you. But this game, this game, it is like a game that was used against me when I was a boy, before the Wall was built.’

‘The huge wall with barbed wire on top that divided the city?’

‘Yes.’ Granddad pauses. ‘You remembered.’

‘It sounded horrible, Granddad,’ I say. ‘How could anyone forget that?’

‘Indeed,’ Granddad says, nodding slowly. ‘Indeed.’

I want to tell him how huge I imagine the wall must be, but I don’t want to interrupt because he’s finally talking about the past again.

‘The government of East Germany was friends with the Russians,’ Granddad continues, ‘so they built the Wall to separate Berlin from the rest of Germany and the countries in the West, like France and Great Britain.’

‘Who built it, Granddad? The people that ran the secret police? The Stasi?’

‘No, it wasn’t the Stasi who built it, although they were a part of it. But it was the East German government, and some say it was the Russians that decided too. They gave the order and the Wall went up overnight,’ he says. ‘I know this because I was catching a tram across Berlin from Spreebogen to see my sister in Heinz Hoffmann-Straße. But the tram stopped in the middle of nowhere. Out of the windows I could see the army telling the driver to go back and in the distance I could see people working in the rain, building a wall and a fence, stretching barbed wire across the top. As they were building it I could see people from the west standing on the other side, not knowing what to do. But I had to get through – my sister was expecting me.’

I lean forward. Granddad’s suddenly talking like he’s there right now.

‘I climbed down from the tram. I thought maybe there was a fault, and that the wall and barbed wire were protecting a new military building. So I walked along it, waiting for it to end, but it stretched on for kilometres, like electricity pylons disappearing into the distance. There was no way through. Everyone was walking around like me, like we were lost. We were lost . . .’

I lean closer.