A long house on Waun Mawn?

The single standing stone near the farm trackway.  Is there a nearby longhouse?

Dave M has been referring in recent messages to the time when he hoofed around on Waun Mawn in 1981, and recorded the presence of what he thought was a long house there.  The details are a bit sketchy, and the only record I have been able to find is in the Dyfed Archaeology Report which summarises work in the Tafarn y Bwlch - Waun Mawn area.    This is a screenshot of the relevant entry:

From the grid reference, it appears that the location is not far from the single standing stone which stands near the Gernos Fach track.  I'll see if I can check it out........