A proposed tunnel for HS2 will allegedly shave 15 months off the current construction timetable.

HS2 also believes it will reduce disruption in the area under Ealing and Northolt where it is planned. The tunnel will be 9 km in length, running from the interchange station at Old Oak Common to Northolt.

It will link to another planned tunnel along West Ruislip with a combined length of 14 km, which HS2 states is longer than those built as part of the Crossrail project.

A HS2 spokesman said: "Our station at Old Oak Common will be a major transport hub allowing passengers to switch between HS2 and the Crossrail connections to Heathrow and the Great Western Main Line."

This announcement comes on the same day Lord Mandelson showed a lack of support for the scheme. The former business secretary said the high speed development was backed by "flimsy evidence" and was originally pushed by the Labour party so as not to be shown up by the Conservatives - who were in opposition at the time - if the latter planned a north-south connection first.