Anyone caught urinating in the wrong place at this year's Glastonbury Festival is likely to have their collar felt by the Green Police.
By Dickon Hooper
BBC News, Glastonbury
Festival guru Michael Eavis backs the work of the Green Police
The environmentally-aware volunteers - 170 in total - will be on hand at the Somerset event to educate and inform revellers about dropping litter and the dangers of polluting nearby streams.
"If you have 200,000 festival goers, there can be a large amount of pollutants passing through the river," said 45-year-old Bernadette Vallely, development manager for the force.
The organisation started about 14 years ago, and now tours UK festivals with the backing of organisers.
"We're comic cops and we aim to embarrass people... and educate them in a humorous way," said Ms Vallely.
"People are approached and we tell them they've been arrested and that they are causing an environmental hazard.
"We don't let them go until we hear the magic words: 'I won't do it again'.
"But we can get people chucked out [of the event], or make sure they never get a ticket again, or take them to the police."
The group, which made 2,000 "arrests" at Glastonbury in 2005, came into its own several years ago when festival organisers were prosecuted and fined after fish died in a polluted stream.
Festival guru Michael Eavis said: "It was fair do's. I deserved it if we were contaminating the stream."
Although he puts the incident down to a faulty and leaking toilet, Mr Eavis supports the Green Police in their work.
"Some people are past caring - they are having such a good time - it is not foremost in their minds not to pee in the hedges," he told BBC News.
"They need reminding. We're very fond of our rivers and streams."
Mike Dunning, from the Environment Agency, said his organisation checks the waterways before and after the festival, and has remote equipment in place which would pick up a surge in pollutants.
"We support the Green Police and are in regular touch with the organisers," he said.
"But we take a softly softly approach - we have come a long way since the incident with the fish. There are better toilets now..."
But could they shut the festival down if things got out of hand?
Glastonbury is the biggest festival the Green Police patrol
Theoretically yes, said Mr Dunning, there is that "remote possibility".
"To be honest though, if there was a serious problem, the organisers would fall foul of their licence.
"This would kick in before we would shut them down."
And if the Green Police are not deterrent enough, Mr Eavis has his own, more natural way of keeping revellers in line.
"We do allow nettles to grow along the river banks. It is a sensitive area..."