I could tell something was wrong as soon as I walked into the 6th form common room. It wasn't like in a Western. It was subtler than that. No one stopped playing piano in the corner. Mostly because we didn't have a piano (we were an underfunded comprehensive school after all). Similarly, no one paused in the middle of their card game to slowly swing their heads towards me in unison like a herd of adolescent cows.

It was a ripple, a pressure front precipitated by my entrance that swept across the room in a wide arc. Its progress was tracked by a shuffling of chairs, the rustle of crisp packets, the raising of hairs on arms and necks. In fact, no one looked directly at me at all.

But everyone suddenly knew I was there. They were all pretending not to know and at the same time had sort of collectively decided to make it really obvious that they did. I don't know, it was confusing - teenagers are weird. I saw Clare Favreau, in the corner by the vending machines, lean over and from the corner of her mouth breathe a long tract of smoke out the open window. It seemed accusatory somehow. Clare was cool.

That's not the point.

The point was that I'd never commanded this sort of attention before. The good kind or the bad kind. Cecelia Martin was very much an average student kind of girl. I wasn't good at netball. I didn't get straight As in class. But neither did I get bullied (much). I existed in the middle, like most people did, I guess - neither covering myself in glory, nor the butt of every joke and hurled insult. I kept myself to myself. I had a small group of friends. We hung out on the balcony in the school hall at lunch times. We volunteered to arrange the chairs before assembly to get in out of the cold playground on early mornings. We played role playing games and made stupid videos which no one subscribed to ever. I was unremarkable and I sorta, kinda, actually really liked it that way.

Now it was as if I was some kind of EMP device that rendered the brains of 17 year old students suddenly inert. And I had detonated as I walked through the ancient swing doors of the porto-cabin that housed our temporary common room.

I shifted the strap of my backpack and scanned the room for Oby. She was sat all the way over against the far wall and absolutely, positively staring at her phone (and definitely not in any way at me). Tension radiated from her jaw. I think I heard the grinding of her teeth from where I stood by the door.

Eyes down, I walked quickly across the room to where she was sitting and threw myself down beside her. She scooted over a little to give me some room, her eyes still on her phone. I tilted my head forwards so that my hair hung down either side of my face, giving me a wildly ineffective privacy screen.

"What?" I said without preamble. That was the way we communicated. We prided ourselves in our directness.

"Not here," breathed Oby, still taking an inordinate interest in her phone. She was playing some janky Candy Crush clone, where you had to match up little blobs of colour with other blobs of colour to make them disappear. Oby firmly believed in not paying for casual gaming and therefore spent a lot of time playing the most dire games imaginable. Even as I watched a giant advert for NOW TV appeared on her screen. "Everyone's watching."

I peeked out from behind my hair barricade again and took in the room. It still didn't seem like anyone was watching but some animal instinct inside me was screaming the opposite. The same ancient part of me that would have kept me safe from sabre-toothed tigers and poisoned berries. It was something about the level of background noise. There was a constant low-level of conversation but no one seemed to be concentrating on what they were saying. It was as if they were all just saying MURMUR.

Murmur, murmur, murmur.

It was ... unsettling.

"Then can we go somewhere that's not here?" I hissed through my teeth. I had leant further forward and was absent-mindedly running a finger around my heel where a blister was threatening to form.

All the blobs on Oby's phone suddenly exploded before being replaced with an advert for Loot Crate. Disgusted, she threw the phone back into her bag.

"Let's go," she said.

The brook was only three minutes from school grounds. It was a tiny little stream thing that ran mostly underground beneath our town's parkland but emerged for a short stretch beside an industrial estate - a Ford car garage, a KFC, a shop that sold tiles, I think. The sides of the brook were lined in sloping concrete and it disappeared into an equally concrete tunnel as it headed out of town. It had become the de facto place for kids from my school to sneak out and go smoke.

And do other things that adolescents do (if the smell of carbon monoxide and slightly stagnant river water struck you as aphrodisiacal).

Oby and I sat with our backs to the tunnel wall, just inside the entrance so that a line of daylight cut diagonally across out knees. The triangle of sun made my legs feel oddly warm, even though it was a mild day out. We were alone. It was too early in the day for most people to be taking a trip to the brook.

Oby had refused to speak the whole way down. Now I turned to her, positively bursting with curiosity.