Anglian Water's chief executive, Mark Thurston, was denied his annual bonus of £1.05m for the 2025-26 financial year after a significant raw sewage spill contaminated the River Mardyke in Grays, Essex. The incident, which occurred on 25 August 2025, saw almost 3,500 tonnes of untreated sewage enter the river, leading to the deaths of at least 4,723 fish.
The Environment Agency classified the spill as a Category 1 incident, its highest classification for pollution events, indicating major environmental harm. Among the aquatic life killed were critically endangered European eels, pike, perch, and carp. Investigators noted that the actual number of fish deaths was likely higher due to difficulties in searching parts of the watercourse.
Investigation reports obtained under the Environmental Information Regulations revealed that an alarm from the Corran Way pumping station was ignored due to an oversight. The alarm was triggered when a valve, which should not have, automatically shut, diverting untreated sewage into the river. The Environment Agency estimated the sewage was discharged at an average rate of 55 litres per second over at least 18 hours.
The decision to withhold the bonus follows new government legislation, the Water (Special Measures) Act 2025, which grants powers to the Water Services Regulation Authority (Ofwat) to ban bonuses for water bosses who fail to meet environmental standards. Anglian Water confirmed that no performance bonus was paid to its chief executive for 2025/26, stating that customers expect executive pay to be linked to performance.
However, Thurston did receive a "retention payment" of £500,000 in July 2025 and a Medium Term Alignment Plan (MTAP) payment of £451,440 in the same financial year. Anglian Water stated these payments were not linked to company performance, were permitted under regulations, and were not funded by customers.