This is reference 6 of the wikipedia entry on Penwyllt and the whole Thesis is online. It is
Helen Mathews, “Penwyllt Village, Growth, Development and Decline”. Local History Dissertation, Univ. Wales Swansea (1991), page 58, “The Potter Dynasty”.
My great great grandfather David Potter was highly literate and lived as a warrener in Cefn Cul when he first arrived from Worth in Sussex, in one of the wildest houses of the area. He married my great great grandmother Rachel (known as Rahel) Morgan of “Y Deri” in Callwen, on March 17th 1856. At the time of the marriage Rachel Morgan was living in Blaen Twyni and David, a labourer, at Tafarn y Garreg. David Potter’s extensive diary is kept in Brecon Museum. My great grandfather William John Potter was born on Dec 3rd., 1856 at ten past six in the morning, so was an early riser. David was buried in Callwen on January 2nd., 1892, Rachel on Dec. 11th., 1907. William John Potter died in 1929, aged 72, at 3 Powell Street, Penwyllt. The Potters were central to Penwyllt, and David Potter was a fine singer, opening many concerts. So he must have known Adelina Patti and her family well.
Stuart Davies has an extensive knowledge of the Morgan Potter Dynasties and may be able to comment on these facts. We know that the family lived at one time in Pen y Foel, a thirteen acre holding outside Penwyllt. I tried to find it recently but could find no trace of a foundation, but it is certainly well known, situated in a very wild and beautiful mountainside over looking Glyn Tawe.