'There was screaming and distress, but also an eerie kind of calm'

I normally drive from BBC Television Centre to my home in Newbury but this weekend, after presenting Five Live Sports Extra's coverage of Wales against South Africa, I decided to catch the train.

I normally drive from BBC Television Centre to my home in Newbury but this weekend, after presenting Five Live Sports Extra's coverage of Wales against South Africa, I decided to catch the train.

I was one of the first passengers on the 5.35 to Plymouth when its platform was announced at about 5.10pm and I remember walking down the platform thinking it was quite strange that the standard class carriages were at the rear of the train with first class at the front ­ normally it's the other way round. For no reason at all I decided on carriage B and sat myself towards the front of the carriage with my back to the direction of travel.

All was going well until about six minutes after leaving Reading. Suddenly there was a violent braking and my immediate reaction was that someone had pulled the emergency cord. The carriage started shaking from side to side and the mild groans that accompanied that early braking suddenly became panicked shrieks. Eventually we stopped. And then there was darkness.

At this stage it's difficult to quantify time. There was obviously distress and there was definitely screaming but combined with that there was also an almost eerie calm. I tried to stay composed but my mind was racing. People were shouting that we should stay on the train and that if we got off, trains in the opposite direction might hit us. But I could smell fuel and thought to myself I must get out. Some people just stayed in their seats totally motionless.

I was very near the door towards the front of the carriage and walked towards it. I couldn't open the door, but the window was open so I heaved myself up and, feet first, climbed through it down on to the track. The carriage was derailed and at an angle but it hadn't turned on its side. Carriage B had been lucky.

I must have been one of the first to get off because there was only one other person I could see when I got outside. I remember treading on mangled metal as I walked towards him.

We both had mobiles so phoned 999. Then I went back to help a girl through the window I'd got through. She was sobbing. Bit by bit, windows were smashed, escape routes negotiated and people started getting off the train. The first blue lights arrived about 10 minutes later and then those of us able to were led on foot to a pub. And now the questions have begun. What if I'd not been in carriage B? What if standard class had been at the front of the train as it normally is? It hasn't sunk in yet.

Jonny Saunders is a presenter with BBC Radio Five Live.