I write this diary at night, either in the toilet, where the rest of the men assume that, like them, I’m wanking, or in bed, with a torch, where they assume that I am ‘some kind of religious nut’. I’m in no hurry to correct them on either count because the less interest they show in it, the better. Often, I sleep with it at the foot of my bed, under the blankets. In the morning, during the ritual of washing and shaving and tidying the barracks, I squirrel it away in the little suitcase that lives under the locker. We all have our secret places. Most of them are respected. The only way anyone would find this diary is if I gave them a reason to look for it – and that I will not do.

Today we had basic anatomy, the first part of our medical training. Thirty of us in a classroom, windows closed, stuffy, the chalk squeaking on the blackboard as the corporal outlined a skeleton, in white. I did it much better in my notebook.

‘And this one?’ He tapped the board with the chalk.

‘The thigh bone,’ we chorused.

‘Connected to?’

‘The shin bone.’

‘And what’s this?’ Tap tap tap.

‘The knee bone.’

‘Thank you, Airman Wright. We can do without the accompaniment on paper and comb.’

‘Yes, sir!’

Wright is the class clown, a loudmouthed Welshman, always at the centre of a gang. He has a big, square skull, a full mouth, and a good build – I noticed him yesterday, of course, the loudest of the lot, showing off, showing his arse, whistling and shouting and doing handstands while he was waiting in line.

The corporal picked up his red chalk, and made a blob somewhere in the middle of the chest. We began again.

‘What’s this?’

‘The heart.’

‘And what does the heart do?’

‘Belong to Daddy?’

‘Thank you, Wright. Anyone else?’

‘Beats?’

‘Good. And why does it beat? Anyone? No?’ He drew a thick red line from the heart to the head. ‘It pumps blood around the body.’

There was a general ‘aaah’, as if this was news to most.

‘Taking oxygen to the brain, to the limbs’ – more thick red lines – ‘and to all the vital organs.’ He picked up his blue chalk. ‘And bringing deoxygenated blood back to the lungs, where it will be … I see I’m going too fast.’

The mysteries of circulation explained, the corporal selected his pink chalk.

‘Now, the muscular system.’

Whistles from the audience, and a bodybuilding pose from Wright, who sprang to his feet and started modelling in the aisle.

‘Here we have the arm muscles,’ said the corporal, at work on the blackboard.

‘Biceps, sir.’

‘Correct …’

‘Then the triceps, deltoids, pectorals, latissimus dorsi, trapezius …’

‘Thank you, Wright. As you seem to know so much about it, perhaps you’d like to come up here and do my job for me.’

‘I’ll do better than that, sir.’ He started unbuttoning his tunic. All heads were turned towards him, apart from Poynter, who sat in the front row, staring fixedly at the blackboard. I could feel sweat breaking out on my forehead – but it was very warm in the classroom.