That area is pretty much on the edge of Rodborough common. I think the stone was "vandalised" shortly after being "rediscovered"
or rather was stripped of vegetation which might explain the secrecy. There is a report published about the stone with a map of it's location which places it in the Bownham Park estate towards the south end. I haven't
had a chance to get back to Stroud to try to find it
since I saw the map .