Heathrow Airport expansion – Supreme Court Appeal briefing

Press release
Briefing prepared by Will Rundle, Head of Legal and Katie de Kauwe, Lawyer at Friends of the Earth
  Published:  05 Oct 2020    |      4 minute read


The historic decision of the Court of Appeal on 27 February 2020 means that the expansion of Heathrow Airport has been halted. Friends of the Earth brought its case against the building of a third runway to protect the climate. Heathrow Airport is already one of the largest emitters of carbon dioxide in the UK. The climate impacts of the airport and a new runway would have been extremely dangerous for people and the planet.

This briefing:

  1. summarises the Court of Appeal result
  2. gives an update on the Supreme Court stage
  3. describes the potential outcomes.

"The legal issues are of the highest importance. The infrastructure project under consideration is one of the largest. Both the development itself and its effects will last well into the second half of this century. The issue of climate change is a matter of profound national and international importance of great concern to the public – and, indeed,  to the Government of the United Kingdom and many other national governments, as is demonstrated by their commitment to the Paris Agreement.”

(Court of Appeal judgment, para. 277)

The Judicial Review and Court of Appeal judgment against Heathrow Airport expansion

The Airports National Policy Statement (ANPS) is the policy framework, created under the Planning Act 2008 by the Secretary of State for Transport to allow expansion at Heathrow Airport. It directs how any development consent application should be decided.

Section 10 of the Planning Act requires the Secretary of State to contribute to sustainable development with particular regard to mitigating climate change.

Friends of the Earth argued the Secretary of State failed to consider:

  • the Paris Agreement on climate change,
  • the non-CO2 warming impacts of aviation, and
  • the climate impacts of the operation of the airport beyond 2050.

Friends of the Earth argued that the ANPS  and decision were unlawful on each count, because they each breached section 10 of the Planning Act 2008, and also the Strategic Environmental Assessment Directive (regarding the Paris Agreement only).  A strategic environmental assessment is a key tool in assessing environmental impact and achieving sustainable development. The purpose in law is to achieve a high level of environmental protection with a view to promoting sustainable development.

Legal action charity Plan B Earth ran a separate argument that the failure to consider the Paris Agreement breached section 5(8) of the Planning Act 2008.

The Court of Appeal agreed with both claimants on all climate arguments advanced. The ANPS remains of no legal effect unless reviewed – it is effectively a “zombie policy”.

The Supreme Court stage

A hearing at the Supreme Court between Friends of the Earth, Plan B and Heathrow Airport Ltd took place on 7-8 October 2020.

The Secretary of State did not seek permission to appeal and dropped out of the proceedings. So too did developer Arora Holdings. Heathrow Airport received permission to appeal the result at the Supreme Court, and that was the case that was heard. Without the government in the picture, the appeal was even more clearly about established commercial interests vs climate justice.

Summary of arguments

Heathrow Airport Ltd  sought to challenge all four of the climate grounds advanced by Friends of the Earth, and the one ground brought by Plan B. The arguments centred on whether the government was legally required to consider the Paris Agreement, the warming impacts  of non-CO2 emissions, and overall climate impacts for the full lifetime of the project beyond 2050 (the target date in the Climate Change Act).

Heathrow Airport also said that even if the government had acted unlawfully, the overall outcome would essentially be the same if the decision were taken again (ie, the ANPS would still be designated). Consequently, the court should not prevent the ANPS having legal effect now in its current form (the remedy ordered by the Court of Appeal).

Heathrow Airport invited the Supreme Court to overturn the full result and attacked both factual and evaluative judgments made by the Court of Appeal, based on what the Secretary of State said. However, the Department for Transport was not involved in the hearing to explain what it did and how it took the decision. Furthermore, the Secretary of State had previously confirmed (at court) that it would not argue that the ANPS would be the same if it had taken into account the matters Friends of the Earth raised.  


Essentially, Heathrow Airport’s case amounted to:

  • Paris Agreement: denying the agreement was part of government policy at the time the ANPS was designated, or that it is necessary to take it into account over and above the Climate Change Act when designating the ANPS under the Planning Act 2008, contrary to what the Court of Appeal found.
  • Non-CO2 warming impacts of aviation: similarly denying these impacts were required to be considered, because it was rational not to do so, because of uncertainty over their precise calculation, and that the “precautionary principle” did not apply.
  • Post-2050 climate impacts: that the Climate Change Act and its 2050 target were all that were required to be considered and that these emissions were already quantified.
  • Strategic Environmental Assessment: asserting that the Paris Agreement was not relevant and the Court of Appeal was wrong to find it was necessary to take it into account.
  • Rationality: asserting that the government had acted rationally in all these respects by discounting them, and it was wrong for the Court of Appeal to find it was irrational and so unlawful on this basis too when designating the ANPS.

Potential outcome

There is no onward appeal from the Supreme Court.

If any one of the grounds that won in the Court of Appeal remains, and the Supreme Court agrees that the Order made should still stand, then the ANPS will remain of no legal effect until reviewed. The Secretary of State must then consider if they wish to leave that result undisturbed or review the ANPS policy framework.

If the Secretary of State reviews the framework, they will likely need to make changes that materially alter what the ANPS says.  Such changes will need to be approved by Parliament following consultation, before the new ANPS can come into force. Even if the review were to be superficial, if Friends of the Earth’s Strategic Environmental Assessment ground remains intact, a new strategic environmental assessment and consultation on it would be required, because the previous one was unlawful for not considering the Paris Agreement.

If Heathrow Airport overturns the full result of the Court of Appeal, or persuades the Supreme Court that no remedy should have been given by the Court of Appeal despite finding the ANPS is unlawful, then the current ANPS will be reinstated. Heathrow Airport could then make an application for development consent, and the battle against expansion would move to the planning arena.

End notes:

  1. Friends of the Earth were represented by David Wolfe QC (Matrix), Peter Lockley (11KBW), Andrew Parkinson (Landmark), and Leigh Day LLP.
  2. The London Boroughs (including the Mayor of London) and Greenpeace Ltd. They were all unsuccessful on appeal. Their case has now been dismissed.
  3. The Airports National Policy Statement is one NPS. Others cover energy, waste, water, and transport. A list is on the Planning Inspectorate’s website