Jarvis has since pulled out of rail maintenance work

The firm pleaded guilty on Monday to breaching safety laws before the incident at Aldwarke Junction near Rotherham on 10 November 2002.

The judge at Sheffield Crown Court said the repair error broke rules known to "every child with a train set".

The HSE inspector who investigated the derailment said the track was "unsafe".

It was an incident that could have been prevented by simply following the railway's own rules Stephen Bates, HSE inspector

The accident in November 2002 came after a locomotive and two wagons were diverted onto a stretch of track with a rail missing.

Jarvis engineers had temporarily replaced a crossing section with a single straight rail but had failed to lock points to seal off the incomplete line.

Investigating HSE inspector Stephen Bates said: "This train derailed because after urgent repair work a section of track had been returned for the passage of trains in an unsafe condition.

"While we were pleased that no injuries resulted from this incident the circumstances were such that people - whether at work or travelling as passengers - could have been hurt as a result."

Poor communication

Mr Bates said the investigation uncovered deficiencies with the way the company, Jarvis Facilities, planned and carried worked out.

Inspectors also found that some staff were not competent to carry out the work and that vital information was not given to them.

"It was an incident that could have been prevented by simply following the railway's own rules," Mr Bates added.

Jarvis was fined �400,000 and ordered to pay �28,000 costs by the court after admitting failing to ensure the health and safety of someone not in their employment - a train driver.