On 5 October 1999, two trains collided at speed in west London, killing both drivers and 29 passengers. Barrister Greg Treverton-Jones, who survived the crash and worked on the harrowing inquiry, pieced together what went wrong

• Warning: this article contains graphic descriptions of injury and trauma

There was no warning and no screech of brakes – just a huge bang, and then we were crashing. I was sitting with my back to the direction of travel, towards Paddington, and felt the impact through my seat, as well as hearing it. For a moment or two, it seemed that we might be all right, because the train continued on its way. But then we derailed, and the wheels started to plough over the sleepers and through the ballast beside the tracks. I became aware of a bright yellow light over my right shoulder, and realised that it was a fireball. It moved along the outside of the carriage from front to rear, and then was gone. The carriage tilted to its right and, out of the window to my left, which was now below me, I could see one or two small fires. A body drifted slowly past that same window. It was that of a middle-aged male. The body was intact, and the man’s eyes were closed. I was struck by the peaceful look on his face as he rolled slowly below us. I remember hoping that he was not hurt, and wondering where on Earth he had come from.

Back then, in 1999, by a strange coincidence, I was acting as junior counsel for Great Western Trains Ltd at the public inquiry into the Southall rail crash, which had taken place two years earlier, in September 1997, and killed seven people. Many weeks earlier, I had been chatting to Richard George, managing director of Great Western Trains Ltd, about his experience as a passenger in the Southall crash. He had demonstrated to me how he had got out of his seat and crouched in the aisle as the train had slowed.