Thames Water is the UK's largest water and wastewater services company, responsible for supplying water and treating wastewater in most of Greater London and surrounding areas. It serves about 15.5 million people, providing 2.5 billion liters of drinking water per day and treating 4.6 billion liters of wastewater. The company has a long history dating back to the early 1600s with the New River Company and has evolved through various public and private ownerships since then. Thames Water operates significant infrastructure including the Thames Water Ring Main and the Thames Tideway Tunnel, which became fully operational in 2025 to reduce sewage pollution in the River Thames. However, the company is currently facing serious challenges, including huge debts, infrastructure leaks, and pollution issues. It has been fined a record £122.7 million by Ofwat, the water regulator, for failing to prevent frequent sewage spills and for making multi-million-pound payments to shareholders despite poor environmental performance. Thames Water's storm overflows have been found to spill routinely, not just in exceptional circumstances. A consortium of investors recently proposed a rescue plan including debt write-offs to help stabilize the company financially.