‘You are in fine voice,’ Mr Clark says, gesturing for silence with flattened palms, ‘but might I suggest you start doing your best impression of diligent students, what with the impending visit from one of our great leaders. Perhaps we could actually get going on those revision timetables that you were supposed to be doing this afternoon.’ There’s a unanimous groan. ‘Come on, books out.’

The shuffle of bags and the graunching of furniture is the perfect camouflage. Amit is turned away from me. There’s no time to check if anybody else is watching. I drop to my knees.

It’s like my hands are working without instruction from my brain. Imagining this moment so many times has programmed my body. There’s no shaking in the fingertips, no panic-stricken fumbling, just efficiency. The drawstring falls slack. The pillow within unfolds. The lid of the plastic tub is cracked open. I can smell the dust from the match heads – sharp and bitter. There’s a red strike in marker pen on the timer dial, another on the housing at the thirty-minute mark. With one small snick, the two are aligned. Without the dial leaning on the switch as it does at the zero point, the detonator is now open-circuit.

My thumb goes for the flash button on the camera, arming it for when the shutter is pressed. This is always the riskiest part. Any fault with the hardware and this single act would fire the bomb. No time now to do it at arm’s length as I always did with the development models. Not that it would make any difference anyway. If this blows, I die. There’s no delay, no fear. I hit the switch. Over the ruckus around me I hear the upward ultrasound shriek of a flashbulb charging. My own chest rises with the sound. This is good to go. The lid snaps back on. The pillow descends. I snatch out an exercise book. The bag is sealed. I’m back sitting at my desk. It’s like I just watched someone else do it.

Amit gives me a nod as he settles into his chair next to me. I smile back. I’m just waiting for silence to fall now, and I’ll get myself excused.

I turn from him and my face falls. I’ve made an error.