AN ambitious plan to build a high-speed rail line north of London via Heathrow – relieving the pressure for a third runway at the airport – is being drawn up by Arup, the influential engineering firm.

Arup has a history of originating big transport projects. In the 1980s it came up with the scheme to route the high-speed line to the Channel Tunnel via Stratford in east London, ending a planning impasse that had threatened its construction.

The Heathrow scheme is in its early stages, and has no official backing from government.

Its first public airing is likely to be tomorrow at a parliamentary reception to launch The Right Line, a book on the history of the high-speed link.

Mark Bostock, a director at Arup and one of the key individuals in the battle over the routing of the Channel Tunnel line, said: “There is total logic in seeing how Heathrow can be connected to the national and international rail network.

“This is fundamental to the sustainable development of the airport and would be a step-change beyond [airports operator] BAA’s extremely modest ambitions for shifting passengers from road to rail,” he said.

Arup’s plan would see the Channel Tunnel line extended west, parallel with the Great Western line. After Heathrow, trains would turn north along the alignment of the Chiltern line, running to Birmingham and Scotland.

“What this plan brings is connectivity – not only bringing the north and the Midlands onto the international high-speed rail network, but also bringing Heathrow within two-and-a-half hours of central Paris,” Bostock said.

The plan would also free capacity at Heathrow by cutting the need for short-haul flights to Europe. This could detract from the justification for a controversial third runway at the airport, plans for which were outlined by the government 10 days ago.

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