I was so angry after visiting this, the last stop of the day. Some idiots had set a camp fire within about 8 feet of the stones (see picture). The ashes were cold, but didn’t look as if they’d been rained on, so were obviously recent and fresh. In addition, one of the rails of the surrounding fence had been broken, presumably during the camp’s high spirits.
On the positive side, I learned something new. This was originally though to be the remnants of a stone circle, as shown by a plaque at the base of the terrace.