When she first suggested work for the government, I was still recovering from an exercise with the 4th Battalion, Parachute Regiment. My feet were swollen and blistered to the extent that I was forced to wear flip-flops. I remembered sitting in her office like that, my PhD proposal in her hands, wondering why she seemed uninterested in it.

‘This is all fine and I think you would do it well. I wondered if you’d thought about other options.’ She put the sheets down as if they’d left her unsatisfied and would do the same to me. ‘You volunteer in the reserves,’ she said.

Even while I sat there with bare feet and a bruised cheekbone, it surprised me that she knew this.

‘Yes.’

‘Do you enjoy that?’

I had joined as a gesture against the comfort of the college, the equation of learning with physical ease. And because it seemed an entirely unlikely thing to do. The training felt like the shedding of skin, which reminded me of learning a language. I had spent my first months at the university impersonating those around me, fascinated by their ready-formed personas, their postures and ensconced positions in networks that appeared to have arisen spontaneously. I had practised stretching my vowels, relaxing them as if I too was relaxed, letting my voice sink back in my jaw. I borrowed the grandeur of the college itself like a costume.

But, to my surprise, it was the army reserves where I excelled. The Brecon Beacons, where most of the training took place, was beautiful and desolate. Ten-kilometre runs became 20 with packs, became 50-kilometre marches with strapless carbines, two hours’ sleep in a damp bivouac then 50 more. It became clear that they were not interested in your strength so much as your weakness. To know someone well enough to stake your life on them, you needed to know where and when they’d break. But you could only break if you were whole to start with. The art was to divide yourself in advance – from pain, primarily, your own and others’, and then from fear. The training, which had seen two men die in the previous five years, was both a border in your life that you were challenged to cross, and an ineradicable partition within you once you had done so.

I enjoyed map work, and even weapons training, which I approached as you’d approach a class on Japanese wood carving – an intriguing skill you would never actually need. I remembered the meditative way in which a visiting commander with sunburnt cheekbones and sun-bleached hair unrolled a black and white keffiyeh which held an MP5 rifle, and arranged the pieces on the scarf, cleaning them, slotting them back together. When he had finished there was the faintest scatter of sand on the Cambridgeshire floor. I looked up. He was watching me looking at the sand. He winked.

‘Yes,’ I said to my supervisor. ‘I enjoy it.’