Kendal Calling 2012.
I usually love the festival, but the security was ridiculously tight and heavy handed, and the organisation was a bit poor. Toilets were horrid, even by festival standards. They stopped letting people bring in alcohol after the first day for absolutely no reason leading to people getting drunk in the car park instead which caused even more problems. Still had a good time, but running out of booze after two days and being given the option to either drink in the car park or pay ridiculous prices in the arena was an absolute bummer. Ended up sharing what booze we had left with the neighbours.
To be fair though they made it up the next year where the stupid policy was reversed, the toilets were better, more options for alcohol in the arena including reasonably priced Real Ale and the security were actually friendly and helpful.