Planning application for Grimshaw’s Heathrow airport expansion to cost up to £800m, airport says

By Tom Lowe2026-05-26T10:41:00

Grimshaw-architects-MAIN-PIC-HEATHROW-CGI-CMYK

Legal fees and environmental impact modelling have seen cost of paperwork almost double since project was paused in 2020

The cost of the planning application for Heathrow’s third runway is expected to surpass £700m by the time it is submitted next year, according to the airport’s latest estimates.

Heathrow Airport chief communications and sustainability officer Nigel Milton said around £400m had been spent on the planning process before the Grimshaw-designed project was paused in 2020 over legal issues relating to the 2015 Paris climate treaty.

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