I laughed out loud. It felt good, even if it did cause dust to fall into my mouth. I tried to spit it out, but as I turned my head to the side I starting giggling again. A little warning bell in my head went off and I remembered that euphoria is one of the warning signs of hypoxia.

Along with impaired judgement – which might explain what happened next.

I conjured a second werelight and had another look around my concrete coffin. To maximise my chances of getting some air I wanted to punch a hole upwards, but not so close to me that if I brought the roof down I would be under it. I chose the top corner on my right on the far side of the rebar portcullis and ran through my impello variations in my head. Impello, like Lux, is what Nightingale calls a formae cotidianae, meaning that generations of Newtonian wizards have poked and prodded and experimented and found lots of fun variations which they then pass on to their apprentices who pass them on to theirs. The hardest thing to learn about magic is that it’s not about wishful thinking. You don’t make an invisible pneumatic drill by picturing it in your mind. You do it by shaping the correct variation of impello, lining it up in the right direction and then essentially turning it on and off as fast as you can.

No doubt there was a fourth-order spell, of elegant construction, which would have served. But I didn’t know it, and when you’re buried under the ground and running out of air you go with what you’ve got.

I took a deep breath, which didn’t satisfy the way it should have, and smacked my drill into the corner. It made a satisfyingly loud thumping sound. I did it again, then again, trying to get a rhythm going. Dust spurted with each impact, falling slowly as a haze in the still air. I stopped after about twenty strikes to check progress and realised that there was no way of measuring it.

So I started banging away again as dust thickened and my breathing got shorter, and then suddenly there was a thud just behind my right eye and everything went dark. Sweat broke out on my face and back and I was suddenly terrified that I’d done something irreparable. Had I just pushed myself into a stroke? Had I gone blind or had my werelight gone out? In the pitch dark it was impossible to tell.

I didn’t dare conjure another werelight for fear that I’d give myself another stroke – if that’s what had happened. I lay still and pulled funny faces in the darkness – there didn’t seem to be anything wrong with either side of my face.

Then I realised I was breathing deeply and the air smelt fresher. So at least the drill had worked.