Infrastructure Planning Blog

Today’s entry reports on the Secretary of State’s decision to make the Gatwick Airport DCO, and briefly summarises the new guidance on flood impacts.

 Lift off

And on the seventh day, the Secretary of State granted development consent for the expansion of Gatwick Airport. This is, as far as we can tell, the first DCO to be granted on a Sunday and it’s a really meaty decision indeed. Here are a few things to note in the decision.

First, there is an important point to make that this decision follows a “minded to approve” letter issued earlier this year. This now-final approval letter should stand as a clear articulation of the benefits of “minded to” letters in that the Secretary of State has now, on many significant issues, shifted from taking the Examining Authority’s view on things to taking the promoter’s – showing that time, and opportunity, may heal wounds. It may seem trite to say, but “minded to” letters are preferable to refusals or unexplained delays.

Second, perhaps unsurprisingly, one of the most contentious issues related to noise. The ExA appears, following its own analysis which was not put to the promoter, to have rustled up their own noise contours which the airport would have to abide by. I would strongly recommend reading the applicant’s response to this here. Once you have read that, it is perhaps not difficult to see why the Secretary of State’s position in the minded to letter that they supported the ExA’s proposed noise contours has now been reversed.

Interestingly, the decision letter records (with “What do you mean” by Justin Bieber presumably playing in the office of the Secretary of State): “When the Secretary of State queried this matter with the ExA on 14 May 2025, the ExA confirmed its position and reasoning remained as per the Report, without providing any additional clarification.”

The applicant prevailed not just on the noise contours, but on noise-related schemes. The ExA recommended a requirement to insulate more than 4,000 properties in approximately 4 years. The Secretary of State now agrees with the promoter that a phased approach, with the most affected properties being insulated first in the context of an application process is appropriate. Similarly, the ExA’s requirement that a home be purchased if noise insulation was not agreed has been kiboshed.

Third, on greenhouse gas emissions, an interesting point to note is that the development (which was the subject of the DCO) would contribute 0.657% to the sixth carbon budget, but the airport’s as a whole would be 3.459%. The IEMA guidance says, indicatively, that if a contribution is over 5%, then the effect should be considered significant. The ExA’s views was that with taking into account the latter figure, and uncertainties, this threshold was met. The Secretary of State said it was the lower figure that should be used. That conclusion is undoubtedly correct: the test of significance applies to a “project”, not the whole of the infrastructure which happens to exist. Finch, like an uninvited friend who has outstayed their welcome, rears its head again but commentary on that is for another day.  

Fourth, this decision is another application of the new duty which applies to national landscapes. The ExA concluded that expansion would conserve such areas but would not enhance them. There was no further mitigation required, but in order to satisfy the new duty, a financial contribution has been deemed appropriate. How much? TBD.

The Secretary of State was presented with figures ranging from £250,000 to £4m, and decided that “a figure towards the lower end of that range to be appropriate.. [and] the Secretary of State is currently of the view that a contribution of £750,000 would seem to represent an appropriate figure” but that she has “added a provision to the Order to allow the financial amount to be agreed by all parties (reflecting a similar provision at article 65 of the Lower Thames Crossing DCO)” to allow for the parties to ruminate, and reach agreement.

Fifth, on surface access, the applicant had proposed various mode share targets for public transport and non-highway arrivals. The ExA expressed concern about these commitments in that the remedy for not meeting them was potentially retrospective mitigations. There is now a fall-back, diluting the ExA’s suggestion, that flights associated with the expansion could continue if either the targets are met, traffic remains within the envelope assessed, or agreement is reached with highway and transport authorities. The suggestion that those flights could continue if highway works were completed was put forward by the promoter, but rebuffed by the Secretary of State.

The DCO contains Hillside-proof provisions (article 9) though the drafting is not identical to the precedented provisions, a power to “use any land so acquired for the purposes authorised by this Order or for any other purposes in connection with or ancillary to the undertaking” (article 20) which is broad, as well as the drafting endorsed in the LTC and Luton Airport DCOs affirming that positive environmental changes are permitted (article 1(9)). The Secretary of State has made several deletions where they do not consider the provisions to have been justified or necessary (including provisions relating to direct vesting, notwithstanding that some protective provisions refer to them).

Finally, on special category land, open space was being acquired for the project. Rather than providing replacement land, the promoter provided additional land, and then argued replacement land was not necessary under section 131(5). In this case was driven by the fact that local authorities “have communicated that they do not wish to be vested with the replacement open space”.

The Great Flood (Guidance)

Finally, the Government has updated the national planning practice guidance (PPG) on flood risk, most notably in relation to surface water flood risk.  It can be found here.

In August 2022, the PPG was updated to state that sequential tests (which means steering development away from areas of high flood risk to those with low flood risk) should take into account “all sources of flood risk and climate change”. This was interpreted to include risks of surface water flooding following heavy rainfall, as well as flooding from rivers and the sea.

But whereas flood risk from rivers or the sea needs to be designed around or subject to the sequential test, it was, until the PPG update in 2022, accepted that surface water flood risk could be dealt with through optimal drainage design.  The effect of the 2022 PPG update was compounded by an update to the EA’s flood risk maps in December 2024, which significantly increased the areas at risk from surface water flooding (homes at risk of flooding increased by 43%, for example).  Planning policy was therefore steering development away from areas of surface water flood risk even though it is accepted that there is very often effective mitigation for that risk (indeed, surface water drainage is improved by new development).

The sequential test has been watered down (pun intended) by the latest PPG update. It says:

“Where a site-specific flood risk assessment demonstrates clearly that the proposed layout, design, and mitigation measures would ensure that occupiers and users would remain safe from current and future surface water flood risk for the lifetime of the development (therefore addressing the risks identified e.g., by Environment Agency flood risk mapping), without increasing flood risk elsewhere, then the sequential test need not be applied”.

So, an important albeit dry (tumbleweed) planning policy update, which should hopefully encourage proportionate assessments and outcomes.

This publication is intended for general guidance and represents our understanding of the relevant law and practice as at September 2025. Specific advice should be sought for specific cases. For more information see our terms & conditions.