First swam in there in the early 1970s. Don't tell anyone about it, it might get crowded!
I ran through Rydal Park a few weeks ago and I noticed a sign asking people going to the pool (it's called Buckstones Jump) not to go up the track that is the first half mile or so of the Fairfield route as it's not a right of way. Instead they asked people to go up through the new camping area by the hall.
Had some great days there.