It was about one o'clock in the morning when I heard some of my units being sent to a road traffic collision on the edge of town. People living nearby had rung in after they'd heard the scream of tyres from a vehicle that was out of control and the finality of the crash as it hit a lamppost on the corner of their road.

The noise of that crash marked the death of a young man of nineteen who had everything to live for.

As the team sergeant it was part of my job to attend all serious incidents. When I got there I saw a car in the middle of the road surrounded by police officers from my team and fire fighters working together to free the body of a young man in the wreckage. The roof had caved in above the front passenger seat where he was sat when the vehicle had hit the lamppost, snapping his neck. Meanwhile, as his body lay there, utterly lifeless and still, a massive amount of activity was going on around the car to free him; arc lights, cutters, generators and other engines, a group of local people huddled in their night clothes at a distance with looks of disbelief on their faces…

A paramedic noticed my rank and approached, a look of pessimistic resignation on his face. He too had seen this many times before and I knew that, like me, he would go home in the morning and hope and pray that this would be the last time he would see this, knowing full well that it wouldn't be.

"One dead, boy of nineteen, broken neck. His friend is in the ambulance. Shock. No other injuries. I guess you'll be wanting to speak to him at some point." He nodded towards the back of the ambulance. Inside was another young man, the driver, white as a sheet, motionless, staring at the wreckage in disbelief. Yes, I would want to speak to him, but shock can also be a serious medical condition and I needed to make sure that he was treated first.

As I looked at him I couldn't tell what he was thinking but I bet somewhere in there was the wish that he could turn the clock back, just ten minutes; that's all it would take, just ten minutes. But you can't turn the clock back. His friend was dead, gone forever and it was his fault. But ten minutes ago he was alive and the driver could have slowed down, and he could have thought about what he was doing and he could have realised that racing downhill on an uneven road surface might be dangerous… But that was ten minutes ago and this was now.

Our colleagues from the Road Policing Unit arrived and, as they are specialists in this work, took over dealing with the collision and the driver responsible. This left only one job left for me to do. The worst job. Inform the family.

We had been able to identify him from cards and things in his wallet and confirm this with the driver but until someone close to the dead person has seen the corpse and 'officially' identified it we cannot be sure because we didn't know them. So, we have to go and see family and say things like "We think your son has been killed in an accident." This is doubly cruel for the family because it raises a spectre of hope that it won't be their loved one, it is all a mistake and it will turn out to be someone else, but invariably it isn't and the thread of hope they have clung to is cruelly cut when they view the body at the mortuary.

You may hear people talk about how they dread a knock from a policeman on their door as the harbinger of bad news. At four o'clock that morning it was my turn, with a colleague, to knock on a mother's door and tell her that her son had been killed. I had a huge hollow pit open up in my stomach as the door opened and a terrified woman with a dressing gown wrapped around her asked what was wrong, why were we there? In her heart, she already knew. Instinctively people seem to know.

If I could communicate how it feels to tell someone their child has been taken from them, completely needlessly and senselessly, brutally killed by controllable forces which were out of control because of human error, indifference or inexperience, I would do so in the hope that if it saved just one human life it would have achieved what it should achieve. But words cannot express how it feels to break that news and watch someone crumple and fall in front of you because of something you've said. It is the worst thing I have ever had to do but there must be a massive chasm between that and the utterly hopeless rending grief experienced by someone who is suddenly told that a loved one has been killed. I hope and pray that I never have to go through that.

When I got home that morning I couldn't sleep. I had to tell my wife what had happened because I had to have someone to talk to. Afterwards, I went upstairs and picked up my six-month old son who was just waking up. As I looked into his face he smiled and I started to cry. I couldn't stop it. The thought that my son could be taken from me so quickly and so violently was more than I could bear and I thought of a mother, six miles away, sitting with dignity and patient grief in the waiting room of a hospital mortuary for someone to come and tell her what they were going to do with her dead son, the son who left home last night looking forward to a great night out with his friend, the son who never came home.