The passenger service operated by Avanti West Coast ran through the 5mph limit at 45mph, the UK Department for Transport’s rail accident investigation branch (RAIB) reported.
It happened two weeks after a similar incident near the fatal landslide site in Aberdeenshire when two ScotRail trains sped through an emergency restriction imposed because of further landslip fears.
The incident involving the train travelling between Glasgow Central and London Euston happened at around 12.25pm on Sunday December 20 last year on the west coast main line at Beattock in Dumfries and Galloway.
The RAIB said the emergency speed restriction was in place "because of the earlier failure of an embankment".However, it said 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.
It said a safety digest will be published in the next few weeks based on evidence gathered so far.
A spokesperson for Avanti West Coast said: “We are co-operating fully with RAIB as they carry out their inquiries.”
The RAIB is also investigating why the ScotRail trains travelled at more than double the speed limit between Laurencekirk and Portlethen in another overspeeding incident, on Friday December 4.
They travelled at up to 100mph through an emergency speed restriction of 40mph which had been imposed "as a precaution in case forecast heavy rainfall caused ground movements affecting the safety of the railway".