Works

At first they were just cutting at the ivy with loppers etc - then, just as I went down for a closer look they vanished again (presumably to offload a van full of ivy clippings). Later I heard the sound of a generator and they were doing something more complicated - again, I went down for a look and they'd retreated to their van for a tea break. So this is the best I can do, snapped from the window.

I think they might be approaching the end of the wall where a couple of massive blocks are loose.......