Question: Rhiwallon ap Cynfyn, was a Welsh King, following the 1063 invasion of Wales by Harold and Tostig Godwinson, he was an Anglo-Saxon Earl of which location, that overthrew Gruffydd, Rhiwallon and Bleddyn jointly?
Sentence (from "Tostig Godwinson"): Tostig Godwinson ( 1026 – 25 September 1066) was an Anglo-Saxon Earl of Northumbria and brother of King Harold Godwinson.
Relevant evidence: Yes