“Black William”
Hanged by Llewellyn ap Iorwerth (= Llewellyn FAWR) for alleged adultery with his wife Joan of England.
See http://freespace.virgin.net/doug.thompson/BraoseWeb/family/home.html for a genealogy, and http://freespace.virgin.net/doug.thompson/BraoseWeb/frames.htm for a very interesting history of this famous Norman famliy.