Thanks to all; it's shocking that he's got to this state, isn't it? I don't know how it's happened, but from the moment we saw that poor bag of bones, something fishy was obviously going on.
You are all right, we have been thinking the same thing, that he could be completely different under saddle when fed up. The next realistic thing really, is to walk away. It's a sad situation, but I can't feasibly have him as a charity case. Can only hope that someone is able to take him on and help him out.