7 Steel UK has signed an agreement to supply steel for Heathrow Airport's planned expansion. The United Kingdom government estimates the project, including a third runway, could need up to 400,000 metric tons of steel. The Cardiff-based company has supplied Heathrow for more than 20 years, including steel for Terminal 5. Its electric arc furnace makes steel from 100% British scrap, which cuts carbon emissions. Heathrow promised in 2025 to prioritise British steel. The deal depends on the expansion winning approval.