I used to ab off the top of Malham many years ago, but that was stopped and the bolts were removed from the top.
The story at the time was that the climbers had been pissed off with the number of cavers abbing past them and complained to the Park Authorities, who had agreed to ban it. I later heard that it was something to do with some endangered plant/moss/bird. I'm sure that someone on here will know the real reason.
A couple of year after that they stopped people jumping off the bridge at Kirkby Longsdale. I think that the ice cream seller must have had a hot-line to the police judging by the speed they arrived at. The reason there was something about it being an ancient monument and you couldn't stand on its walls. I asked one attending policeman if I could hurdle the wall to get round that interpretation and he threatened me with 'incitement to commit an offence' because anyone who followed me might touch the walls. :-\
Even longer ago I used to bridge swing from an old viaduct in S.Wales. That eventually gained a sign from the local council stating that the footpath over the bridge was just confined to the middle of the bridge and that anyone hanging anything over the walls would be charged with trespass. I didn't push this one as I gained enough sense not to do such a silly thing again