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"): After being exiled by his brother, Tostig supported the Norwegian king Harald Hardrada's invasion of England, and was killed at the Battle of Stamford Bridge.
Relevant evidence: No