Thinking purely from a practical view, Cecil........... It sounds like you have a brick construction with a brick coping. It's usually perfectly possible to repair, or even take down a wall from your side only. It would have to be done by working "overhand". Quite easily done by anyone who is prepared to work other than "by the book".
I've done it myself a couple of times. It won't look terribly wonderful from his side (acceptable though.) If he doesn't let you in, then that's his problem ;o)