There was (is?) a further cairn uphill from here, to the NNE. If it still exists it’s lost on the verge of a forestry track.
From GGAT:
Carn Buarth Maen (SO0269104854)
Possible cairn, appearing as a low indistinct mound entirely covered with thick tussocks of grass; stone can be felt underneath. Edges most clearly marked at S and E; fade out on N and W. On the verge at the S of a forest ride, at the top of an E-facing slope. Dimensions: ?5.6m diameter; c 0.2m high
(1976) Now in a forestry plantation; nothing could be found (RCAHMW)
(1999) Cairn as noted on OS 6 inch 1st edition 1885 map. No visible presence; possibly destroyed by the FE or perhaps it is located within dense tree cover.