The UK Government will today announce a new Y-shape route for the controversial HS2 project from Birmingham to Manchester and Leeds.
Last night, sources were predicting the Glasgow-to-London journey was achievable in three hours and 38 minutes, down from four hours and eight minutes.
It is also believed HS2 would cut journey times from Glasgow to Birmingham from three hours and 57 minutes to three hours and 22 minutes.
The new £32.7 billion rail project is one of the Government's economic priorities, aiming to rebalance the UK economy with journey times of just 80 minutes between London and Manchester.
The project will be completed by 2033, with no timetable for extending the line to Scotland – although Deputy First Minister Nicola Sturgeon has talked of a Glasgow-to-Edinburgh high-speed link that would eventually be tied in to the English network.
Meanwhile, a legal challenge has been lodged to force the government to reconsider its initial link between London and Birmingham because of concerns over the route.
Trains running on HS2 would be able to run on conventional track too – meaning passengers from Scotland would travel at conventional speeds to Manchester and then at up to 225 mph to London.
Railways expert Dr John Disney, of Nottingham Trent University, said: "This is the first major development of the railway system since Victorian times, so it is a once-in-a-lifetime opportunity."