A fireball swept through some of the express's carriages

Paul Harrhy, 33, a senior driver standards manager of Orpington, south London, says he suffered depression after being told to act as the company liaison officer in the wake of the disaster.

He claimed he had symptoms of post traumatic stress disorder, including nightmares and flashbacks.

An Appeal Court judge decided the case should proceed after throwing out an appeal by Thames Trains against an earlier ruling in the High Court.

Mr Harrhy says he worked long hours and had to spend time in the burnt out carriages and view and deal with bodies.

He says he has not been able to travel on trains since and has not been able to work since March 2000.

Liability denied

He argues that Thames Trains was negligent in that it failed to provide him with a safe system of work and did not give him training beforehand or counselling afterwards.

The company denies liability and says it was not foreseeable that Mr Harrhy could not cope with the job.

Thirty-one people died and 500 were injured when two trains collided at Ladbroke Grove in the approaches to Paddington Station on 5 October 1999.