The Prime Minister launched the UK's first-ever 125mph tilting train today and declared it was a "great day" for the railways.
Tony Blair joined Sir Richard Branson, boss of Virgin Trains, to mark completion of the first phase of a multi-billion pound upgrade of the West Coast line.
Mr Blair joined rail industry officials at London's Euston station for a ceremony to mark the milestone.
A new timetable, being introduced a week today, will cut journey times between London and northern cities including Manchester.
Mr Blair said: "This is a great day for railways in Britain. Passengers on the West Coast routes will now benefit from the first phase of the investment."
Sir Richard said he had waited five years to see the Pendolino trains tilting at speeds of 125mph.
He said: "Today is a very emotional day both for myself and the rail industry which has finally made it happen."
Brian Souter, chief executive of the Stagecoach Group, said: "The West Coast route used to be known as the premier line. Today is a major step in winning back the pride and delivery that goes with that accolade."
Virgin Trains chief executive Chris Green said: "Our new timetables and faster journey times will bring the regions closer to London and support the regional regeneration of Britain."
Journey times between London and Manchester will be cut from 2hrs 41mins to 2hrs 6mins, a 22 per cent reduction. Today, on its record-breaking run, the train reached Manchester just one hour 53 minutes after leaving Euston.
Further improvements on the line in December will improve journey times between London and other cities, including Liverpool and Preston.
Further upgrades next year will accelerate journey times to Glasgow and Edinburgh.
There was strict security at Euston station for the Prime Minister's visit.
Platform 16 was closed to the public while Mr Blair spoke to invited guests and the media.
The West Coast main line is Britain's busiest rail route and has been upgraded at a cost of £7.6 billion.
Since May 2003, a 9,000-strong workforce has worked a total of 24 million hours to rebuild the railway between London, Birmingham, Crewe and Manchester.
An army of engineers has installed more than 460 new sets of points, 600 miles of overhead wiring and more than one million tonnes of ballast.
Ian McAllister, chairman of Network Rail, said: "This is a significant achievement and marks a massive step forward in the continuing modernisation of the West Coast main line.
"Passengers along the route have been incredibly patient as we have practically ripped up the route and rebuilt it.
"But the benefits are considerable, with faster, more frequent services and more to come as our task to rebuild Britain's railways continues."Reuse content