Funky wall....

On my way back to the tube after dropping work off at flow I came across this rather interesting curved wall. I assume that it is this way because of the growth of the tree pulling it upwards, but perhaps the wall had to be laid this way due to the tree pushing up the land, or perhaps it is a mis-match of the two, some sections of it certainly do look like a patched-up jigsaw! Who knows, but I think it's quite unusual: