Windermere

The analysis, which the BBC had exclusive access to, used United Utilities operational data to establish when the company was discharging sewage into Windermere when it should by law have been treating some of it.

Regular discharges of sewage into Windermere have been blamed for increasing nutrient levels and turning parts of the lake green – so called "algal blooming."

The BBC has regularly reported on discharges into Windermere.

The longest illegal spill the analysis identified was for 10 days from Hawkshead pumping station, which flows into Windermere via Cunsey Beck.

The latest analysis covers four years of data from six sites that discharge sewage into the Lake Windermere catchment.