Tree Pruning or Tree care, the following picture is a perfect example of why, "If you are a tree owner you should have a tree care program for your trees"
This Robinia - Robinia pseudo acacia is a mature tree, it has been in place for a minimum of forty years and quite obviously never been thought of as a problem or thought of as "somebody elses problem".
there are literally only a couple of options here, the owner has to change the construction of the wall if the tree is to remain and not be felled.