Here's a thing: Apparently 'Sow' was the term used to describe the wood and hide constructions used in the attack of fortified buildings during the middle ages. The kind of thing that would be built to stop the defenders pouring boiling pitch etc. Maybe this Black sow isn't a pig. Maybe it's something that was used to attack a peel tower somewhere in the area, or even, at a right stretch of the imagination, Edlingham castle.
The grid reference for the holed stone is: NZ 0463. 9867
Its on the north eastern side of the beacon.
The chaps who are investigating it are calling it. "The Beacon Solar Observatory" and work is on going.
Thats interesting, about the construction for protection when attacking pele towers etc. It is a possibility.
It would be help full to find the full version of the ballad.
Some one who I spoke to said that in the ballad a priest from Holy Island tried to convert the black sow to christianity. In which case it may have been a reference to pagan beliefs..as in the tailess black sow in Welsh mythology....the plot thickens!