The pair were due to attend a preliminary hearing in the City of London Magistrates' Court last Thursday. But the case was delayed for six weeks and is now due to be heard in January at a date yet to be confirmed.

They each face a criminal charge for a breach of Section 3(1) of the Health and Safety at Work etc Act 1974. The HSE alleges that by failing to adequately install or maintain the railway line, the companies exposed people to unacceptable risks.

The prosecution centres on the incident on Sunday 24 November 2002 when the leading bogie of the fifth coach of a First Great Western, Swansea to London express derailed East of Southall station.

It travelled a further 1.6km before coming to a halt just before West Ealing station.

At the time of the derailment, the train was carrying 450 passengers and travelling at approximately 120 mph. All carriages remained upright and no passengers or staff were injured as an immediate result of the incident.

The maximum penalty in the Magistrates' Court for a single offence of breaching Section 3 of HSWA is a fine of up to £20,000. It is open to magistrates to commit cases for trial or sentencing to the Crown Court, where the maximum penalty for the same offence would be an unlimited fine.