One of their gardeners had had a go at it, but he wasn't one of the ones who'd been on the course, and it really was just some stones (and a piece of wood, perhaps meant as a seat) placed on the top of the wall. It still looked quite nice, but perhaps more rockery than dry stone wall.
First thing was to take off the new stones, and then remove and set aside the original top 'cope' course of large flat stones, to be replaced after the wall beneath had been made a bit taller.
After lunch it clouded over a bit, but the rain stayed off, and by about four o'clock I'd got the new course in and replaced the copes.