Supreme Court gives green light to third runway at Heathrow

Backdrop to the appeal

Earlier this year, the Court of Appeal ruled that the planned expansion of Heathrow Airport was unlawful. In particular, the Court of Appeal determined that the Secretary of State for Transport had failed to take into account climate change obligations contained within the Paris Agreement on Climate Change (the Paris Agreement) when drafting the Airport’s National Policy Statement (the ANPS).

Whilst the Court of Appeal confirmed that it was not necessary for the ANPS to conform to the Paris Agreement, it did consider that the Secretary of State was required to take the Paris Agreement into account in a way which could be both evidenced and explained. Following the Court of Appeal’s decision, it was expected that in order to pursue the expansion of Heathrow airport, the government would need to revisit the ANPS with a focus on considering and, to the extent possible, adhering to, its commitments on combating climate change.

The ruling and rationale

Following a recent appeal by Heathrow Airport, the Supreme Court has held that the decision taken by the Secretary of State for Transport regarding the expansion of Heathrow Airport was, in fact, lawful.

Section 5(8) of the Planning Act 2008 provides that a national policy statement (such as the ANPS) must explain how it takes into account government policy relating to the mitigation of climate change. Whereas the Court of Appeal had found that the term “government policy” should be construed as “necessarily broader than legislation” and could include previous comments made by Government ministers, the Supreme Court considered that the term should be given a “relatively narrow meaning.”

Whilst the ANPS did not make specific reference to the Paris Agreement, the Supreme Court held that the Secretary of State had taken the contents of the Paris Agreement into account, including carbon targets and budgets, and he was not legally required to give it more weight than he decided was appropriate. The Supreme Court’s decision therefore paves the way for a planning application to now be submitted for a third runway at Heathrow Airport.


The direction of travel, in terms of the UK’s commitment to combatting climate change, is clear. Indeed, the UK Government has recently committed to reducing emissions at the fastest rate of any major economy with a 68% reduction in greenhouse gas emissions by 2030 in order to set the UK on course to be carbon neutral by 2050.

Significant future infrastructure projects in the UK, particularly in the energy, transport and waste sectors, are likely to face similar scrutiny as the expansion plans at Heathrow Airport. Planning and development consents are unlikely to be granted for such projects if these are seen as incompatible with environmental law and policy. Going forward, construction professionals working on such projects will need to have close regard to the latest policy commitments on combatting climate change in order to avoid lengthy and costly legal challenges.

As to Heathrow itself, whilst the path has now been cleared for a planning application to be submitted, there are still numerous hurdles to be overcome before a third runway is formally approved. A public enquiry will still need to be convinced that there is a case for expanding Heathrow and ultimately, the UK government will be given the final say. Whilst the expansion of Heathrow does represent one of the biggest planned infrastructure projects in the UK, the impact of COVID-19 on the aviation industry has also brought into sharp focus the question of whether the necessary demand for increased capacity is still there. This will all be set against a backdrop of continued legal challenges with environmental groups already intimating that the expansion plans will be challenged at every stage, including by way of an appeal to the European Court of Human Rights.

Related item: Impact of the Heathrow decision on the construction industry

Related content