In the eerie silence after the Apache helicopter left, we realised we were on our own

together in circumstances that might, at any moment, end any of their lives, and sometimes the simple rules of civility melt away.

It isn’t that you want to be cruel, rude or cause offence. But the tension can explode out of you in myriad ways, and releasing some of it by ranting and raving, goading and taunting each other, is something that men in combat situations have done throughout the centuries.

‘Do you think it’s appropriate?’ I was asked. This time, I didn’t answer. I don’t know how many times I was shown the snippet of video that day.

By the time we were done, we seemed to have been through it frame by frame.

As I watched and answered what questions I could, the memory rose up from all the thousands of others I’d locked away of my time in Afghanistan.

I remembered the sound of the Apache helicopter’s rotor blades as it had charted its course overhead, before loosing the power of its chain gun and slicing the insurgent down.

But I still had little idea where the video had come from, how it had come into their possession and whether the ‘ war crimes’ they stipulated were based purely on the things they had seen and heard here, or on other evidence as well.

(I wouldn’t discover until much later the video’s provenance. One of the lads we’d been on patrol with that day, a relative newcomer, had secreted a tiny camera in his helmet to take personal footage, which he later shared with friends. One of them had a bitter falling out with his wife, the police became involved and they seized the man’s laptop. In scouring it for evidence to substantiate her allegations of violence, they found this snippet of video from our patrol in Helmand Province.)

Back in the solitude of my cell, I reflected on everything I’d seen. I wondered if the other marines who’d featured in the video had also spent their days in police cells, being asked the very same questions over and over again. Or perhaps, because I was the ranking officer that day, it was only me being asked to explain.

That same afternoon I was released without charge — but I was left under no illusion that this wasn’t the last time I would be questioned.

As I was driven home, I had this ominous sense that the madness and the tensions of Helmand were reaching out for me even now, beneath beautiful English skies. WHEN the police dropped me off at home, I stalled momentarily before entering. I had been in so many life-threatening situations during my military career in Iraq and Afghanistan that they had almost become normal. But even when sitting in a desert compound under rocket attack, I never got the sinking feeling in the pit of my stomach that I had now.

The video had triggered in me recollections of that day in Helmand, and as I’d been driven home I’d been drawing all the disparate pieces of it back together.

In the next few moments, I was going to have to re-live it all for the benefit of the most principled and pragmatic person I know and the person who loved me more than anything else in her world — Claire.

I tried to formulate the words to explain that it really was a war crimes charge I was facing — to explain to her what took place that day in the desert and the disjunct between the man in the footage and the man I had always held myself to be.

There have never been any secrets between Claire and I. It is one of the foundation stones of our relationship. I had never lied to her about my time in Iraq or Afghanistan, but that was a mark of how little I’d dwelt on that day in the desert.

In fact, I hadn’t give it another thought after we returned to our compound on the night it happened. Now it all came flooding back, and I had to get it off my chest.

‘Claire,’ I began, ‘There’s something I have to tell you.’ I told her how we were 200 metres from the safety of our compound and holding our defensive position in the undergrowth when we were given the shot insurgent’s grid reference and ordered to go and retrieve his weapon.

It took an hour moving slowly and methodically to guard against IEDs buried in the ground before we reached the field where he had been gunned down. Up above, the Apache helicopter was still circling the area on the lookout for other insurgents. There were more Taliban out there — whether near or far, we didn’t know.

From the shelter of some long grass, we scanned the field and I caught sight of the shape of a body lying out there in the middle, with his weapon next to him. Going to him would be risky. We’d have no cover if anyone was out there.

But we had our orders and the quicker we got this done, the better. I turned to Jack, one of the lads, and said, ‘You’re with me.’ Then, turning to the rest of the patrol, I said, ‘Stay sharp, boys. We may be coming back at a run.’ Hoisting our packs onto our backs, Jack and I took off into the field.

When we got to the insurgent, there was no doubt in my mind that he was dead. He was lying in a pool of his own blood and gore, the earth steeped in the fluids that had pumped out of his body when the Apache’s chain gun opened up on him.

Steeling myself — because you never truly get used to handling the dead — I got down on my knees and began searching him for any other weapons. The sheer amount of viscera repelled me. We marines had also been warned about the risk of catching blood-borne infections from casualties in the field.

‘But the second I put my hands on him,’ I told Claire, ‘he opened his eyes.’

Until that moment I had not considered the possibility he might be alive. Not a breath had come from his lips, nor the merest twitch in his body. Yet now his eyes were open. There was no lucidity in them, but his eyelids fluttered and came apart, and that meant that some corner of him still clung on.

How I will never know. There was a huge cavity in his back and his lungs were hanging outside his body.

My immediate reaction was frustration and anger. Not because he was alive, but because it meant that now, instead of quick march back to the security of our compound, we would have to get this man, critically injured by our own ordnance, out of this field and to a military hospital.

I radioed a message up the chain of the command, telling them the insurgent wasn’t dead. Somehow, we would have to clear a landing zone, call in a casevac (casualty evacuation) helicopter and load him aboard.

I looked around me. The cornfield was littered with shrapnel. There may even have been IEDs hidden around us as well as other armed insurgents. Any of those things could frustrate a helicopter landing.

For now, though, what we needed was shelter, and I called over two of the other guys to carry him to the edge of the field. They used the ‘two-man drag method’ we’d been trained in, hooking their arms under his armpits and heaving him along. It wasn’t gentle, but it was competent, safe and quick.

We reached the others, laid him down and attempted to stabilise him, dressing what wounds we could and making sure his airways were clear. But there seemed to be no movement whatsoever from him.

On the video footage they showed me in the police station, I’d heard the dark things the lads were saying, the gallows humour, how we joked about finishing what the gunner in the Apache helicopter had started and getting out of there.

In the quiet of that police station it had seemed so brutal to me. Out there, in those fields, on those patrols, in our base under rocket fire, I thought so little of it. By now, the Apache had gone, and the silence around us was deafening.

A helicopter hanging above makes you feel more secure, knowing any insurgents will think twice about springing an ambush on you. In its absence, all that remained was the pervading sense that we were out here on our own.

I looked at the insurgent, the lads clustered around him administering what medical aid they could, and it all seemed so pointless. There were so many holes in him.

Any casevac helicopter would take a full half hour to get here, and I couldn’t even call one in before I’d found and cleared a landing zone. Meanwhile, the radio was still crackling with the news that other insurgents hadn’t been accounted for. The lads, still teenagers some of them, were increasingly jumpy.

And so was I, for all my years of experience. You hold it together, because that’s what you’ve been trained to do. But I was scared.

There were Taliban somewhere out there, and yet here we stood, hidden by nothing but long grass, attending to the body of a mortally wounded insurgent who, only a couple of hours ago, had been launching an attack on our neighbouring compound.

I looked at him again. What scant signs of life there had been now seemed vanishingly rare. There was no way he was making it back to any military hospital alive. It was a wonder he had lasted this long. There was nothing more we could do for him. ‘He’s dead, lads,’ I said. I got on the radio, reported this back up the command chain, and waited. Then waited some more.

Back in our sitting room in Taunton, I looked at Claire.

‘And then I shot him.’

MARINe A by Alexander Blackman is published by Mirror Books, price £20. To order a copy for £16 (a 20 per cent discount), visit mailshop.co.uk/books or call 0844 571 0640, p&p is free on orders over £15. spend £30 on books and get FRee premium delivery. Offer valid until April 16.

The moment I touched him his eyes flicked open There was no way he‘d make it to hospital