Damning reports suggest extending the HS2 tunnel through the borough would lower the cost of the project and ‘reduce its devastating impact’ on residents.

Hillingdon Council has commissioned two independent studies looking into the viability of an HS2 tunnel through the Colne Valley to reduce the impact of the high speed railway on west London.

The council - along with borough MPs, action groups and campaigners - has repeatedly requested the whole route through the borough be a tunnel should the project go ahead.

It said it commissioned the reports - one from development and infrastructure consultancy business Peter Brett Associates (PBA) and the other from economic development consultancy business Regeneris - after HS2 “refused to provide a robust appraisal of the extended tunnel option.”

The line for HS2 is tunnelled through central London but emerges in Ickenham High Road in West Ruislip.

High-speed trains will then travel overground and on a viaduct over the Colne Valley before entering the Chiltern Tunnel near the M25.

HS2 argues a tunnel through the Colne Valley was considered but: “ending the tunnel at west Ruislip offered the best solution from an environmental, construction and cost perspective.”

But without a tunnel people living in Ruislip, Ickenham and Harefield say they are the ones who will suffer with heavily congested roads, noise pollution, 24hour working, construction sites, dumped spoil and the destruction of some of the borough’s beauty spots - with no benefit from stopping stations in the borough.

The expanse of the Hillingdon Outdoor Activities Centre lake will be almost bisected by the viaduct for HS2

The first study, by PBA, proposes a 7km tunnel between West Hyde and West Ruislip as an extension to the proposed Northolt tunnel - replacing HS2 Ltd’s viaduct and surface section plan.

The report says: “There is a feasible tunnel solution which will allow HS2 to transit the Colne Valley in a manner which avoids the extensive work proposed on the surface, the consequent negative construction impacts over a seven year period and the permanent operational noise and visual impacts.”

There are huge technical benefits from tunnelling, the report states, and it will have significantly less impact on the environment, communities and businesses.

It also found the extension would “enable provision of the turnouts in tunnel for a future Heathrow Spur."

It has been argued connections between the spur and the main line HS2 track could not be sited in tunnels, they would have to connect above ground, which is the reason past requests to extend the tunnel beyond Ickenham were dismissed.

The cost of the tunnel was estimated at £1.16billion, 5.8 per cent more than the current HS2 option: “but this does not take account of property or community costs,” the report says.

The second report by Regeneris valued the economic, financial and environmental cost of HS2 on Hillingdon at between £41.9million at the lower end to as high as £157.5m.

Accepting the lower range of impacts, the cost difference between the PBA proposed tunnel extension scheme and HS2’s viaduct scheme reduces to £22.13m - just a two per cent gap.

The council said HS2 has already estimated its compensation costs at over £54m and the reports show the cost of extending the tunnel through the borough would be considerably lower.

Nick Hurd, dad for a sixth time

Ruislip, Northwood and Pinner MP Nick Hurd, who will join the select committee of MPs scrutinizing the HS2 Hybrid Bill when they visit the borough next week, said: “For years now, HS2 have tried to fob us off by saying that a tunnel extension was not feasible or cost effective.

“These reports blow that argument out of the water.”

HS2 boss David Higgins has said his view on the tunnel has not changed. In a letter to Mr Hurd he wrote: “We have never questioned whether a tunnel is feasible but, from an early stage, it was clear that it was not a practicable solution to the challenges in the area.”

HS2 are now working on their own study to find out the consequences of tunnelling under the Colne Valley, which they say ‘reinforces’ their conclusions.

Mr Hurd said: “Instead of using taxpayers money to back up their old excuses, I will be challenging them and Ministers to be open minded and engage properly with the argument.

“If a tunnel extension could be the cheaper option and imposes less grief on the community, then it is their responsibility to look at it very seriously,” he said.