Glastonbury Festival has been ordered to pay a £31,000 fine after human waste from the site polluted a nearby stream.
The incident happened after a steel tank used to store human sewage from festival-goers sprung a leak during the event in June 2014.
20,000 gallons of untreated sewage filtered into Whitelake river and caused harm to water quality and killed at least 42 fish - with a number of protected brown trout and bullhead dying as a result.
Sensors in the stream alerted the Environment Agency - which later prosecuted the Somerset festival's organisers - that ammonia levels had increased.
Glastonbury Festivals Limited admitted a single charge of breaching environmental regulations at a hearing in January.
District Judge Simon Cooper, sitting at Bristol Magistrates' Court on Tuesday, fined the festival £12,000 and ordered it to pay £19,000 towards prosecution costs.
The judge found Glastonbury Festival had "low culpability" for the incident and praised its response and systems following a two-day hearing.
An alarm for ammonia levels in the water was activated at about 11pm on June 28 in 2014 but the cause of the leak was not established due to difficult conditions of thick mud, vegetation, darkness and festival-goers at the site.
The festival was criticised for waiting until 6.34am the next day to alert the Environment Agency, with Judge Cooper saying they would have been "unimpeachable" if they had called immediately.
The festival's failure to alert the agency through a hotline resulted in an eight-hour delay and caused a "serious deterioration" in water quality, an Environment Agency spokeswoman said.
The festival's organisers appeared in court on five occasions in connection with the incident and the court heard the prosecution has cost the Environment Agency £34,236.81.
Speaking outside court, Michael Eavis said the case against them has been "a bit of a waste of time".
He said: "It's a great result and I think we were listened to fairly.
"I don't really think it was necessary to get this far. We pleaded guilty to make it easier for them yet they still wanted to pursue this case.
"I think it was a bit of a waste of time, to be honest with you. It wasn't that serious a crime really.
"We did our very, very best when we found the leak - we really did all that we should have done within the timescale.
"This wasn't really necessary. We should have been doing something else. We're putting together the biggest show in the world in four weeks' time."
Glastonbury Festival's turnover in 2014 was about £37m but its net profit was about £84,000 due to its level of charitable giving.
Mr Cooper said the company had given £8.7m to WaterAid, Oxfam and Greenpeace over the past eight festivals.
The sentence took into account an incident in 2015 in which a contractor believed that tanks for the long drop toilets were linked and waste got into the water course.