£500m Thames Water desalination plant has provided just seven days’ water over 15 years

Plant in Beckton has run only five times and has been beset by multiple problems since it was built

London's desalination plant has cost more than half a billion pounds since 2010 and has run only five times, delivering 7.2bn litres of drinking water, roughly seven days of London's typical daily demand. Now Thames Water is planning a new 500m project to tackle drought in the capital.

The Thames Gateway desalination plant at Beckton, built for 270m and now largely mothballed, has racked up an estimated 200m in debt interest, about 45m in idle upkeep and about 3m in operating costs, according to Thames Water figures. That puts the lifetime bill at about 518m, or about 7p for every litre the plant has ever produced, which is 28 times more than customers usually pay for their water.