Upgrades are under way, with the aim of getting 50m litres of water a day [Ml/d] by the end of the current five-year investment cycle and “75Ml/d during drought periods” by 2031, according to the water company’s documents.

A Thames Water spokesperson said the Gateway desalination plant is designed to provide up to 5% of London’s supply “during very dry conditions”, with decisions on operation based on long-term forecasts and storage levels. Once safety works and maintenance are complete it will run “in line with our water resources management plan”.