I follow Zannah’s instructions: park in the visitor car park, text Murad’s phone to say I’ve arrived. Immediately, three dots appear on the screen beneath my message. She’s typing. Or he is.

Nearly a minute later, the typing is still going on, or so the jumping dots indicate. Maybe it’s both of them together. What are they doing, writing an essay?

The message that finally lands has no name at the bottom, so I can’t tell who wrote it. It contains directions for how to find the Art room on foot. The school has 2,000 pupils and is spread over four buildings if not more. Each one is a labyrinth of corridors. I’m to meet Zannah at a particular door, which she’s waiting at.

What’s she doing in the Art room, when she gave the subject up two years ago? She’s supposed to be at a History revision day. And why can’t she come and meet me in the car park?

I cross the wide rectangular yard and knock on the prescribed door when I find it, planning to ask all these questions. Zannah’s voice calls out, “Mum?”

“Yeah. Open the door.”

“I can’t. There’s an intercom, and I don’t know the code.” Her face appears at the window next to the door, which is open. She opens it wider. “Quick, climb in.”

“What? Are you kidding? I’m nowhere near agile enough to—”

“Mum, it’s a ground-floor window. It’s easy. You might not be able to do it gracefully, but you can do it.”

“All visitors are supposed to go through reception. If someone sees me . . .”

“They won’t. Why d’you think I chose this room? In Bankside Park terms, this is the middle of nowhere. No one’ll see you, unless you take four years to climb in.”

“Can’t you climb out?”

“No! Someone might see us together. Just do it, now.”

I manage to get inside, but not quickly and not without injury. I land inelegantly on the large table that’s pushed up against the wall beneath the window—perhaps by Zannah, to catch me—then roll onto the floor. The room I land in doesn’t look like an Art room. It looks disused, like a semiderelict space awaiting redecoration. There are no pictures up on the peeling walls.

“Please tell me this isn’t really the Art room,” I say.

“Was. This whole block’s unsafe or something, so it’s going to be done up. Oh, my God, have you ripped those trousers?”

“And grazed my knee.” I bend down to inspect it. “Do you want to tell me why these indignities were necessary? It had better be good, Zan.”

“Have you watched it yet?” she demands.

“Watched what?”

“You haven’t!” She looks aghast. “I emailed it to you!”

“I was with a client, then rushing to meet you. I haven’t had time to check my emails.”

“Get your phone out,” she orders, nodding at my bag. “You need to watch it now.”

“All right, but . . . can you calm down?” Her rapid-fire manner makes me think someone’s going to burst through the door at any moment and try to kill us both.

“Calm down, yes. Slow down, no,” she says. “It’s a time-sensitive situation. You’ll need to log into school Wi-Fi, there’s no 4G here. It’s BanksideParkStaff, no spaces, capital B, P, and S and the password’s—”

“Wait, there’s no . . . Oh, I’ve got it. Password?”

“banksideparkers, no spaces, all lower case.”

“Okay. Done. How do you know the staff Wi-Fi password?”

“Everyone knows it. Solid spy network.”

I go to my email inbox, open the message from Zannah and click on the link that’s the only thing in it.

It’s a video clip of extremely poor quality, with muffled, shaky sound. I can just about make out Zannah’s jeans and trainers, the ones she’s wearing today, and another pair of legs that also end in Nike trainers—red ones that I recognize, with orange laces. “Is this you and Murad?” I ask. Zan nods. They’re allowed to wear their own clothes when they come in for revision days.

In the film, Zan is laughing, telling Murad that he’d better put his panini away because “She’s coming. I can hear her.” A close-up of the panini fills the screen for a second. Then we’re back to the trainers.

“It’s fine,” I hear Murad say. “S’a revision meeting, not a lesson. No one’s ever said we can’t eat in those.”

Zan laughs. “Hosmer’s going to say it in like, five seconds. No eating in classrooms.”

“No, it’s no eating in class,” says Murad. “This isn’t a class, per se.”

“Oh, per-say?” Zan giggles. “Just put it away! Seriously, you want to provoke Hosmer? Why give her the chance to make your life a misery when you know there’s nothing she likes more?”

“I’m hungry.”

“Is it just you and Murad at this revision class?” I ask Zannah.

“Yeah, these sessions are voluntary. Everyone else was a no-show. And you think I’m unmotivated. Shh, listen.”

“This is going to be brutal,” says Recorded Zannah. “I’m going to film it: your blood dripping down the walls after she’s cheffed you. Here we go. Too late to back out now!” There’s another wobbly shot of the panini, then gray fuzz, then Murad’s trainers again.

“What’s that on the desk?” I hear an Australian voice ask.

Camilla Hosmer: head of History and a walking, impossible-to-solve, pros-versus-cons dilemma. She’s conscientious, well organized and expert at transferring knowledge of her subject from her brain to her pupils’ brains, which can’t be said of most Bankside Park teachers, unfortunately. She’s also a vigilant and passionate enforcer of every tiny rule on every single occasion, even if it makes no sense. The word “flexible” is not in her vocabulary. Murad knows this better than I do. I suspect his panini stunt is a deliberate attempt to entertain himself and Zannah by winding her up so that there will be less time for History revision.

“It’s a panini, miss,” says Murad in the video clip. The visuals have disappeared. I think I’m looking at the underside of a desk: just semidarkness with a few bumpy imperfections in it. “Bacon, avocado and Brie. It’s delicious. Want some?”

Deliberate cheek. This isn’t going to end well. I’m fairly sure that my being here is something to do with the forthcoming unhappy ending to this little scene. Cheers, Murad. It’s not like I need to earn money or anything.

“This is a revision session, not a bistro,” I hear Miss Hosmer say.

“But, miss, I’m starving.”

“Get out! Now.”

“All right, I’ll put it away, miss.”

“I told you to get out, Murad.”

“But look, I’m putting it in my bag. There, it’s gone.”

“Take it out of your bag, put it in the bin and then. Get. Out.”

“Miss, I’ll go if you really want me to, but I’m not throwing my panini away. If I do that, I can’t eat it later, can I?”

“How would you like it if I told your parents I’d caught you eating a bacon sandwich?” Miss Hosmer snaps at him.

“What do you mean, miss?”

Murad says something else, but I can’t tell what it is. Zan’s voice obscures it; she whispers something.

“You know what I mean,” says Hosmer. “You’re letting yourself down, and you’re letting your family down.”

“Why? Because he’s eating bacon?” Zan’s voice. She sounds angry.

“Oh—do you think my family’s Muslim, miss?” Murad laughs. “My dad kind of is. But my mum isn’t. She’s whiter than you, and a hippie. And we all eat bacon.”

I look up at Zannah. “Fucking hell,” I say.

“Watch,” she orders.

Her recorded voice in the video says, “Why have you turned bright red, miss? Is it because you’ve realized you’ve messed up and you owe Murad an apology?”

“Throw the panini in the bin, and then leave this classroom, please,” says Hosmer. She doesn’t sound angry anymore, just cold and remote.

“No, I won’t,” says Murad. “I’ll leave if you want me to, but I’m not throwing my lunch away.”

“And I’ll leave too, but only once you’ve apologized for your racism,” says Zannah.

“I haven’t got a racist bone in my body, Suzannah.” Hosmer sounds tearful now.

“It might not be a bone,” Zan quips. “Maybe it’s a racist intestine.”

“Or a kidney,” Murad says.

I nearly drop my phone when there’s a sudden burst of loud noise. Miss Hosmer has started to shout in a hysterical way that borders on shrieking. I can’t make out her words but it’s something about going to the head teacher right now. The clip ends abruptly, while she’s still in the middle of yelling.