Tilting trains will finally be able to run at up to 125mph on the entire section of a busy London to Scotland rail route from next week, it was announced yesterday.

The tilting Pendolinos were originally intended to run at 125mph on Virgin Trains' West Coast route in September 2002.

This date was pushed back to May 2003 and then slipped further as the giant £8 billion West Coast modernisation project ran into difficulties.

Yesterday Network Rail (NR) said the completion of the next stage of the upgrade work on the line would mean Virgin could operate the trains at maximum speed between London and Glasgow from next Monday.

Until now, Virgin has only been to run the Pendolinos at 110mph on certain sections of the line.

The extra speed will mean London- Glasgow journey times will come down from five hours to four and a half hours, while London-Manchester will take just two hours.

NR chief executive John Armitt said: "The completion of this major piece of engineering work is more evidence that Network Rail can consistently deliver the largest scale projects."

"Most importantly, passengers are now starting to reap the benefits of all the nights, weekends and holidays that our engineers have worked over the past few years."

NR is now working on further improvements on the line to increase capacity and journey times by 2008. These include:

* A £300 million scheme to double the number of lines through the Trent Valley

* A £190 million project at Rugby to relay track and rebuild the station

* A £200 million project in the north west between Sandbach and Wilmslow in Cheshire to replace the signalling system.