‘What are you writing?’ says Troy, trying to look at the page. I hide it with my hand, like when you don’t want anyone to copy your spellings in primary school. All I’ve written is Lucas didn’t say no when.

I hope Troy didn’t see. He’d assume this was going the way of my friendship with Marco, which I can barely remember, though Troy will, very clearly indeed.

Marco isn’t in our tutor group. I’m sure I never see him beyond the occasional glimpse of the back of his head today, and that must be why I can hardly even picture him now. I wish I could. He made me have feelings.

Throughout the rest of the day I ask people if they’d murder me if they could get away with it, and a surprising number of people don’t say no. A few say yes, but I think they’re just trying to be funny. I write it all down.

I’m in maths when I remember the other thing. Ariel did find something: Gus has a girlfriend and two children. Gus! He’s thirty-seven. Ariel saw him out for a run and took a photo. It all comes into my head at once, as if I’d opened a door and found them all on the other side of it. Coco and Zara. My nieces. A woman called Abby Fielding.

I have no idea how I’d forgotten that, or why I’ve remembered it now. I know that I can’t just sit here, trying to solve simultaneous equations. I have a bit of power, even if it’s tiny.

I stand up. Mr Patel looks at me. When I say, ‘Gonna be sick,’ he gestures to the door.

‘Go with him, Troy,’ he says. I shake my head.

‘I’ll be fine,’ I say, and I dash out of the room, and, to make it convincing, into the boys’ loos.

Troy follows anyway: I’d have done the same. I run into a stall and lock it, and think about making vomit noises, but what’s the point? I flush, then come out and give him a shaky smile.

‘You all right?’ He pulls himself up on to the window sill, but his feet still nearly reach the floor. The room is echoey, clattery and smelly. The window is frosted and smeared with grime. All the stalls are open.

I nod and say, ‘No’.

He says, ‘I knew it. Go on then.’