The one I was referring to is Longcliffe Quarry (which I have mentioned on this forum previously, having used it on some of my longer training runs). Much used for rock-climbing https://www.thebmc.co.uk/modules/rad/view.aspx?id=2204 , also this https://www.youtube.com/watch?v=f_czA4j-zjk , or simply lazing around by the "poolside" on sunny Summer days. Now fenced off, much of it with high industrial fencing (but there are ways through), with an impenetrable fence across the track that leads down to the only "beach"; which means that if you jumped in, you wouldn't be able to walk out unless you could scale the fence.