Heathrow Airport’s third runway plan, that involves re-routing and tunnelling the M25, has been given Government backing as the basis for expansion going forward.

A second option featuring a smaller runway put forward by Arora has been rejected.  

Heathrow welcomed the decision to press ahead with the 3,500m long runway, saying it would bring economic and passenger benefits. 

Critics have previously lambasted the idea saying it would make a mockery of climate targets and the motorway works – as witnessed with the long-delayed A3 M25 interchange works – would bring parts of Surrey to regular standstills.

Heathrow says the M25 re-routing works would take place on land next to the existing motorway with the switch made “in a series of carefully planned overnight operations”.

A Heathrow spokesperson said: “Expanding Heathrow will mean more connectivity, increased trade, improved passenger experience and a huge economic boost for the British businesses that will help design and build it. 

“However, we still need further clarity as to how the crucial next phase of the project will be regulated. 

“We need definitive decisions from the CAA and Government by mid-December so that delay to the project can be avoided and we can get on with delivering this vital project for our customers and for the UK.”

The £33billion third runaways plans are expected to be entirely privately funded. It is projected to cost £21bn for the runway work, including £1.5bn for the M25 re-routing, with an additional £12bn spent on terminal infrastructure.

The airport has also said it would be investing £15bn to upgrade and modernise its current facilities. These would include a new terminal ‘T5X’, and expand Terminal 2 and three new satellites.

In 2024, Heathrow handled 83.9 million passengers at 99 per cent of its annual flight capacity of 480,000.

Overall the plans would increase those numbers to 756,000 flights and 150million people.

Heathrow’s expansion plan will now shape the review of the Airports National Policy Statement (ANPS) –  the framework the planning decision will be based on.

The Government said Heathrow’s option was the most deliverable and the most likely of the two to be granted before the next general election.

The Department for Transport said it did not represent a final decision and that any amendments to the ANPS will be subject to consultation and parliamentary scrutiny next year. 

Exact details such as length, layout, and infrastructure implications will continue to be considered throughout the review. 

Transport Secretary, Heidi Alexander said: “Heathrow is our only hub airport which supports trade, tourism and hundreds of thousands of jobs, underpinning prosperity not only in the South East but across the UK.  

“Today is another important step to enable a third runway and build on these benefits, setting the direction for the remainder of our work to get the policy framework in place for airport expansion. 

She added: “We’re acting swiftly and decisively to get this project off the ground so we can realise its transformational potential for passengers, businesses, and our economy sooner.”

The government said the plans must meet the UK’s legally binding climate obligations but needed to be balanced alongside delivering economic growth as well as air quality and noise obligations.  

She added that the independent Climate Change Committee will be consulted to ensure expansion is consistent with the net zero framework. 

The government expects a planning application will be brought forward after the review of the Airports National Policy Statement. 

Heathrow’s promotional video said: “We understand people may be concerned this could cause congestion or delays. 

“Following previous consultation with national highways we have developed a smarter solution.

“We build the future right next to the present. The vast majority of construction happens off-line.

“A new realigned section of the M25 is built on adjacent land while the current motorway operates as normal and the tunnels and bridges for a new runway are constructed while minimising impact on the airport or the existing motorway.

“Then in a series of carefully planned overnight operations, we make the switch. 

“Traffic is transferred on to the new alignment with minimal disruption to journeys.

“Our approach also ensures local traffic and access for surrounding communities are kept moving with minimal disruption. 

“This frees up the old route of the M25, creating a safe, traffic free zone to build the final parts of the runway. 

“The results is an upgraded and expanded M25. Crucially new link roads separate M4 traffic movements from the m25 mainline journeys, easing congestion and creating a safer motorway.”