Although my suspicions were aroused following the subsequent identification of what I’d taken to be unrecorded ‘round barrows’ upon Egsair Rhiwlan (immediately to the SE) as the impact residue of shells from a former WW1 artillery range... it would appear the monument to be found here is indeed the real deal. Sweet.
Coflein has this to say:
“A circular, grassy mound, 7m in diameter and 0.6m high. It has a thin peat cover but slight erosion shows that the main body of the mound is composed of earth and stone. It is located on a flat, broad hill summit, overlooking the Elan valley. When visited in June 2009 the area was used for rough grazing and vegetation cover was grass. [J.J. Hall, Trysor, 9/9/2009]”
If obscure hangs away from the tourist bustle of Cwmdeuddwr are your thing, they don’t come much better for such limited effort than this little round barrow.