I take a deep breath, but I could suck air in like a whale and it wouldn’t help. After our falling out and then making up by the tree, Granddad said that we need to trust each other and that we can talk about anything, but I can’t talk about this.

I sit down beside him.

‘Tell me everything,’ says Granddad. ‘Don’t leave out any details. I’m interested to know everything as I have been stuck in this room.’

I stare at the floor. If I don’t start talking soon, he’s going to guess there is something wrong, and if I tell him about the tournament maybe he will tell me on his own – after all, he’s told me lots of things lately that I never knew. But nothing as big as this.

Eventually my words start to come out. I tell him it took two hours to get to Birmingham and I ate sandwiches and drank plenty of water. And when we got to the school it was massive and looked like Hogwarts and he smiles and tells me he doesn’t know what that is. And as I explain I find myself thinking that he looks too kind and friendly to be a Stasi commander, but then I’ve never met one so how could I know. It would be easier if I’d found out he was a secret Arabian knight that turned into a cheetah or a leopard. At least I could look at his skin for evidence of his spots or stripes. But there’s nothing. Not even a number tattooed on his wrist or hand. He’s just the same old Granddad, who’s smiling at me as I tell him I lost the second game because my opponent was eating Doritos, then nodding approvingly as I tell him the moves I made in the rest of the games.

‘Wonderful,’ says Granddad, leaning forward. ‘Now, the final, tell me about the final.’ He rubs his hands together like he’s warming them by a fire.

This is when I have to tell him I know. After I tell him I used his move, that’s when I tell him I know he’s Commander Steiner. But I can’t do it.

‘It was just another game, Granddad,’ I say.

‘Nonsense,’ he says. ‘A final is not just another game.’

I lump back against the cushions.

‘What’s wrong?’ asks Granddad. ‘Is there something you are not telling me? Did your opponent just concede? This is fine if he did. It means you won the game with your mind.’

‘No, Granddad,’ I say. ‘It’s not that.’

‘What is it then?’

I swallow hard. ‘Granddad, I got cornered, and I was desperate, I was trapped.’

‘And?’

‘And I used the special move: the Yugoslav Attack.’

‘Good,’ says Granddad. ‘But why are you so unhappy?’

I take a deep breath. Then another.

‘Felix?’ Granddad leans in front of me.