SWW was trying to repair a leak at Bishopsteignton pumping station, but effluent began leaking into an estuary at nearby seaside resort Teignmouth.

Beach bathing was banned as sewage equivalent to 10 public swimming pools leaked into the estuary, just as Teignmouth Carnival started in 2003.

It had come from an underground pipe that SWW knew nothing about.

The firm blamed a series of management failures for the incident.

Sentencing at Newton Abbot Magistrates' Court will take place next week.