Me and Jake stop talking. We’re in history getting ready to watch a film about the First World War. I try my hardest to behave in history because I like learning about the war, but also because Mr Keytes is cool. He’s not like some of the other teachers, who just tell me off or send me to isolation. He actually talks to me. I think it might be because he understands, as he never sits down in class.

The classroom turns dark as Harry Giles closes the blinds. The film starts with a black and white picture of soldiers standing in trenches. I try to concentrate, but it’s hard with Jake whispering in my ear.

‘He doesn’t know we’ve figured him out.’ Jake nudges me. ‘Your granddad – he’s just letting it drag on until you give in.’

‘I hope you’re right, if not I could be playing chess for a lifetime!’

‘A lifetime!’ Jake puffs out his cheeks.

‘Yes. That’s how long he says it takes to learn it.’

‘A lifetime? That’s like more than a week, a month, a year!’

‘Lads, come on,’ Mr Keytes whispers as he crouches down between us. ‘You can’t be messing around all the time. We need to improve your grades and this should be really interesting for you both, so just try to watch.’

‘I am,’ I say, glancing at Jake.

Mr Keytes moves away.

On the screen, soldiers dig trenches and set their guns on top of sandbags. The classroom booms with the sound of gunfire.

‘It might not be so bad,’ Jake whispers. ‘It might only be a few years if he means his lifetime, not yours.’

‘Shush!’ I elbow him in the ribs.

On the screen, soldier medics run with first-aid satchels and billycans.

‘Felix.’ Jake holds his side. ‘You need to calm down. It’s not going to happen. There’s no way he’ll go scuba diving.’

‘I can’t. I really can’t.’ My chest cramps. I can’t tell Jake I hate swimming, that I hate just putting my head underwater. I definitely can’t tell him I even wore a raincoat when Grandma took me on the Pirate Falls Log Flume at Legoland.

‘Look at me, Felix.’

‘What?’ I turn to Jake and see his eyes lit up bright in the dark. ‘What are you staring at me like that for? It’s weird!’

‘It’s not. I saw a magician do this on TV. He hypnotized a woman and made her rob a bank.’

‘But I don’t want to rob a bank.’

‘I know.’ Jake waves his hand. ‘Forget I said that, just repeat after me: “My granddad will not go scuba diving.” ’

‘But . . .’

‘Repeat, Felix. “My granddad will not go scuba diving.” ’

I take a deep breath.

‘Okay. My granddad will not go scuba diving. My granddad will not go scuba diving.’

Jake smiles. ‘Feel better?’ he asks.