In reply to JPE:
As Paul says, technically ALL climbing in the First Hydro owned areas is banned. They take a sensible approach of ignoring experienced climbers using the higher levels of the quarries (since those climbers know the risks so the landowner has no liability) but they have to have a sort of "Plausible deniability" - if inexperienced visiting tourists or local kids saw people climbing and "had a go" without understanding the risks the landowner could have some legal responsibility, so climbing in more visible areas is frowned upon - hence the big fences and bolt removals at Dali's hole.
It's more difficult for them to ignore climbing at Llyn Peris area since (a) it's more obvious from the roads/footpaths, (b) it's obvious from their buildings / carpark and (c) its not just an old quarry area, its part of an active "fast response" hydroelectric station. The fact that one of the boulders is called "Underwater boulder" should raise awareness that there are potential risks here!
The correct response is exactly what you did - walk away with no arguments.
Next time try not to be seen....
