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The last few weeks before a General Election is an inauspicious time to launch any new policy let alone one that will cost billions, take decades to deliver and which will only succeed if cross party agreement can be secured.

Yet that's exactly what Transport Secretary Lord Adonis has done.

Lord Adonis wants to build high speed railway lines right up the spine of Britain, linking the country's major cities and punching through some of the most beautiful areas in Britain.

The White Paper detailing the route will be published next month and to symbolise the political consensus he hopes to secure for the project he invited Newsnight on an exclusive tour of Britian's only existing high speed line with two very unlikely fellow travellers - battle-scarred political opponents Lord Heseltine and John Prescott.

We joined Hezza and Prezza on a day trip along what the government now calls High Speed 1 - that's the channel tunnel rail link to you and me.

The 68 miles (109km) of high speed railway between London and Dover seem very modest when compared to the 3,600 miles of high-speed line in operation in Europe, but they would never have been built without the interventions of both veteran politicians.

Despite their ideological divisions (and the fact that Mr Prescott opposed the building of the channel tunnel) both men were instrumental in the construction of the channel tunnel rail link.

As Environment Secretary Michael Heseltine championed the route out through east London, while Mr Prescott was instrumental in saving the route from bankruptcy in the late 90s.

Now together they are supporting Lord Adonis' plan to bring Britain into the high speed railway age with a network the government is calling High Speed 2.

The high speed network he plans would slash journey times to Britain's major cities. Once complete you would be able to zip from London to Birmingham in just 45 minutes, to Manchester in one hour and 20 minutes and up to Scotland in less than three hours. Leeds would take an one hour and 25 minutes and you would be in Newcastle in two hours flat.

The big challenge will be maintaining a political consensus on the issue. Just look at how attempts to get cross party agreement on long-term care for the elderly degenerated into a .

Indeed momentum on High Speed 2 might be maintained by Lord Adonis himself.

There is a rumour in Westminster that the Tories are considering offering Labour's transport secretary the same portfolio if they win the election.

Lord Adonis told me he would not do that, but as our train sped back towards Stratford, Lord Heseltine suggested to Mr Prescott with a laugh and nudge that they might take the brief on together and see the project through.

That is unlikely ever to happen, but it will need a similarly visionary cross party initiative if Lord Adonis' grand vision for Britain's railways is to be rolled out across the country.

Watch the full report on Newsnight, Wednesday 17 February 2010.