An incident in which a steam train passed through a red signal and just missed a High Speed Train on the main line in Wiltshire is now the subject of a criminal investigation.
Rail investigators from the Office of Rail and Road, the Government's railway safety body, are understood to have found "significant weaknesses" in the safety management systems at West Coast Railways after investigating the incident which happened near Royal Wootton Bassett.
On March 7, a steam train on an excursion passed through a red light and only narrowly missed colliding with a passing InterCity 125 train.
The Cathedrals Express service, a special train pulled by Battle of Britain class steam locomotive Tangmere number 34067, overshot the red light by 700 yards at a junction where the tracks to the West split into the line which continues to Chippenham and Bristol Temple Meads and the one for Bristol Parkway and South Wales. The steam special was travelling from Temple Meads to Southend and is thought to have narrowly missed the First Great Western 3.28pm service from Swansea to Paddington, which had just gone through.
It came to rest at the Wootton Bassett junction just one minute after the previous train had passed. Network Rail consider the incident the "most serious" of its kind to have happened on the West's railways in recent years.
Investigators have now decided that they will take matters further with an inquiry to see if health-and-safety laws have been breached and whether a prosecution in the courts could follow.
Network Rail withdrew temporarily the licence it gave to West Coast Railways, the company that runs the steam trains and operates the tours, to run trains on the railway network.
It is the first time any action of that kind had been taken against a company operating trains on Britain's privatised railways.
Now the Office of Rail and Road is considering whether or not to revoke the company's licence completely.
This is alongside the body deciding whether to mount a prosecution under health-and-safety legislation.
A spokesman for the Office of the Rail Regulator said: "The rail regulator has notified the West Coast Railway Company that it is reviewing the company's safety certification – needed to operate trains on the rail network.
"Our initial investigation has found significant weaknesses in the company's safety management systems.
"ORR is carrying out further assessments to determine whether health and safety laws were breached, and the enforcement action required," he added.
A spokesman for Network Rail said: "This decision has not been taken lightly.
"We have set out a number of actions to address the safety concerns raised and will continue to work with West Coast Railways to ensure their services can run safely in the future."