An investigation is under way after a train travelled at 45mph through a 5mph restriction zone put in place due to problems with an embankment.
The passenger service between Glasgow Central and London Euston entered the emergency speed restriction near Beattock, in Dumfries and Galloway, at around 12.25pm on Sunday December 20 last year.
According to the Rail Accident Investigation Branch (RAIB), the restriction was in place “because of the earlier failure of an embankment”.
However, the RAIB added there had been “no adverse consequences as a result of the overspeed”.
The independent body has launched a preliminary examination into the circumstances surrounding the incident.
A safety digest will be published in the next few weeks based on evidence gathered to date.