Harry Potter 'Hogwarts Express' steam train run by Carnforth-based West Coast Railways runs a red light

The incident at Morar on September 10 is reported to have happened close to a level crossing that had its barriers open to road traffic. The train went 20ft beyond the stop board.

The Jacobite is run by West Coast Railways based in Carnforth.

Nigel Harris, former managing editor of RAIL magazine, told the Green Signals podcast “the potential for catastrophe is obvious”. He said the train was on its return run to Fort William, with the locomotive running backwards, as is normal.

Richard Bowker, his podcast co-presenter and a past chair of the former Strategic Rail Authority, said such incidents, which were known as Signals Passed at Danger, or Spads, were taken “very, very seriously because they are a precursor event to something potentially much worse”.

The Office of Rail and Road regulator (ORR) has asked for a report about what happened from Jacobite operator West Coast Railways (WCR).

Mr Bowker said: “It is clear there is risk here and the ORR will officially declare the severity of it once they’ve received WCR’s report on the incident.”

He said the train had stopped between Morar station and the level crossing, whose barriers were raised and its red warning lights were not flashing.

A spokesperson for WCR said: “On September 10, we notified the ORR and Network Rail that the Jacobite passed the stop board at Morar by 20ft. At WCR, safety is our priority, and we are now reviewing the incident in line with standard industry practice.”

An ORR spokesperson said: “We are aware of the incident and have requested a report from WCR to establish the full facts.”

WCR is embroiled in a long-running safety dispute with the ORR over its attempt to continue using carriages for the Jacobite without mandatory central locking after an exemption expired.

The prohibition, which has been signalled for years and is being complied with by other heritage operators, led to WCR losing a court case against the ORR in December. The operator delayed the start of the season in April after applying for a further exemption just weeks before.

WCR has since used a combination of non-compliant carriages with locked-out doors coupled to others which have central locking for the service.