Perhaps this is worth someone taking a look. It stands at the boundaries of the parishes of Aberhafesp, Tregynon and Bettws Cedewain. So it's been said it's just a boundary stone, especially as it's apparently got someone's initials on it. But Coflein boldly suggests "the weathered condition of the stone may indicate reuse of an earlier monument." Their record says it's about metre high, but 1.4m by 0.7m round.