Ok folks, the roof foothold on this was looking loose as a bastard today, held on only by a woodlouse behind it. Deteriorated a lot just on the two goes that I used it, so I coaxed it off to save it getting kicked off and shattering etc.
Someone who's more of a local or regular than I am needs to take a view on whether this needs glueing back on. It came off in one piece, and I stashed it under the first bit of floor level tufa, in the leaves to the left of the problem. It's left a decent foothold, bigger than before, but the rock is shit. Currently has a sharp lip that will crumble when stood in. Will glue back on fine, except everything you're glueing it to is shite. Basically that whole area of roof is crap shattered hollow rock. If everyone avoids that patch of rock it's probably still climbable at the same grade as before.
