A water company has been fined £607,000 for releasing millions of litres of raw sewage into a stream.
Hundreds of fish were killed in the sewage spill in Maidenhead in June 2014, which was followed by a second leak two months later.
Thames Water pleaded guilty to two pollution charges at Aylesbury Crown Court.
The firm said the "regrettable" incidents were caused by wet wipes blocking sewage screens.
An estimated 30 million litres of untreated human waste and other pollutants were released in the first spill, the Environment Agency (EA) said.
Members of the public reported a "grey and odorous cloud of polluted water" from Maidenhead Sewage Treatment Works entering Maidenhead Ditch leading to The Cut river, the agency said.
It said the sewage screens were still blocked three days later.
An unknown amount of sewage was released in a smaller incident in August 2014.
EA manager Colin Chiverton said its investigation had revealed repeated discharges, and failures by Thames Water to react adequately to alarms.
He said: "Pollution could and should have been avoided had the many warnings and alerts leading up to the incident been... dealt with properly."
In a statement, Thames Water said: "Our current pollution levels are 46% lower than five years ago, when this regrettable incident happened.
"We're really sorry for what happened at our works, which has a very good track record, following one of the wettest winters on record.
"This led to higher than expected amounts of wet wipes and other unflushable items getting into the system and causing a blockage."
The firm, which pleaded guilty to failing to comply with environmental permits, was also ordered to pay £100,000 costs.
Previously the company was fined £20m over pollution incidents in Buckinghamshire and Oxfordshire in 2013 and 2014, and also incurred a £2m fine over another Oxfordshire discharge in 2015.