Contractor Amey and rail operator Network Rail have been fined a total of £500,000 after the derailment of a train near Southall, west London, in 2002.

Both companies were fined by the Old Bailey after pleading guilty to failing to properly maintain the track, exposing the train’s 450 passengers to risk. Nobody was injured in the incident in November 2002, in which a train travelling at 120 mph came off the rails.

Amey was fined £300,000 for its part in the incident, and Network Rail £200,000. Both were also ordered to pay costs.

Judge Richard Hone said Amey had not ensured the track was properly maintained, and Network Rail had not supervised the work properly.

The judge said that the accident happened when a metal plate on a crossing split and part of it became lodged in the track. The wheels of one of the eight coaches on the train came off the track as it travelled through Southall station. He added it was “an enormous mercy” that nobody had been killed or injured.

David Morris, deputy chief inspector of railways, said afterwards: “This derailment could have caused a major catastrophe. It illustrates the importance of ensuring that railway tracks are properly maintained to a high standard.”