Banded rhyolite, Newport, Pembs

Three huge chunks of banded rhyolite have been used on the Parrog in Newport as a memorial for Brian Watts, who died in 2005.  They are pretty spectacular -- the larger of the three probably weighs ten tonnes.  I don't think they are glacial erratics -- from their sharp edges, I think they have been quarried from a rock outcrop somewhere in the neighbourhood.  There are a number of rhyolite outcrops on the northern flank of Carningli.   I am trying to discover the provenance........

Text-book examples of contorted flow banding, created by flowing lava and picked out by layers of quartz (?) crystals......  Click to enlarge.

PS.  The provenance will remain a mystery.  Apparently Glyn Rees, the landlord of the Golden Lion in Newport, "obtained" it from a secret location in the year 2000, as a Millennium commemoration stone, and never divulged where it came from.  So the secret went to the grave with him when he died.......