We used to sneak in to the woods of a town park, we were seen, we think, a number of times. One time tho, we had finished, looked over our shoulder and there was some bloke watching through the trees, I am sure he was wanking. Another time, we had finished and were walking back, we passed a member of the public, walking with a park ranger, the bastard had probably reported us, if we got caught, we would have been in the shite!!