The impact was only a matter of seconds in coming, but those seconds felt like minutes. This wasn't how it was meant to be. It wasn't how I had imagined it during my years as a Central line train driver. We talk of "jumpers"; workmates tell of blurry images flashing in front of them, of the shock of the impact. I wasn't expecting to see a young man in jeans and a summer shirt waiting for death, looking me in the eye.

As I hit the emergency brake, I was thinking, "Please, get out of the way. Now. Please let it be a prank." Youngsters on the track are a regular event, though no less frightening for that, and for train drivers it's something we learn to live with.

But this wasn't a typical game of "chicken": he wasn't laughing and he wasn't with friends. When it became clear he wasn't going to move out of the way, I closed my eyes, covered my face and held my breath.

By the time we were stationary, four of my eight cars were in the platform and I was on autopilot. I told the passengers there would be a delay in opening the doors due to an "incident", and was calling the line controller for assistance when I heard a tap on my cab door. A smart man inquired, "Do you know there's a person under your train?" I looked at the blood on the windscreen momentarily before assuring him that, yes, I was aware.

He paused for a heartbeat, looked at his watch and said, "So, how long before we get on the move again?"

I was to look back on this exchange with amusement and also, strangely, comfort: in the midst of the horror, normality was briefly restored by a commuter asking for alternative travel arrangements.

I'd advised the passengers to stay where they were and not to try to open the doors because we weren't fully in the platform; amazingly, they all complied. I walked back through the carriages opening the adjoining doors and shouting: "Please leave the train, and leave the station as quickly as possible!" Terrorist attacks were still very much on people's minds, and as each carriage emptied I looked to the next, seeing anxious faces through the windows. No one tried to leave until I opened the doors. Only a few asked the reason, none complained. I was hugely impressed.

The next few hours were a blur of activity as the body was removed and service restored: station staff, police, firefighters, the emergency support unit and trauma counsellors all came and went in a smooth, well-practised exercise. I was reassured that it wasn't my fault, that there was nothing I could have done; it was his choice. All of which I knew, but it was good to hear from someone else.

As a child of the enlightenment, a rationalist and an atheist, I was sure I wouldn't be unduly affected by the death of a person unknown. I was told I'd need some time off in case of post-traumatic stress; I agreed to counselling to assess my fitness to resume work, but was convinced this would be a formality.

My return to work was speedy and for weeks I was seemingly unaffected. But in August a policeman came to brief me before the inquest and to show me the pictures. The unknown person now had a name, a family and a tragic story.

Henrik Alexandersson had moved from Sweden to find work in London; he was successful and popular, but had been unwell. For some reason, he'd convinced himself his illness was Aids-related and that week he had gone for a check-up to find out the truth. By that Saturday, he could bear to wait no longer: he called his parents in such a state of distress that they booked a flight to London (arriving just hours too late.) He left a suicide note, and headed off for his fateful meeting with me. Had he waited a day longer, he would have learned that the tests were negative.

I left work and went home in the full realisation that perhaps I am not such a rationalist after all, because I sobbed my heart out in the arms of my partner. A year has passed now, but I can still see Henrik standing on the track, awaiting the inevitable.

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