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?

Related documents: [0]  [DOC] Rhiwallon ap Cynfyn (c. 1020 – c. 1069 ) was a Welsh King. the son of Cynfyn ap Gwerstan and brother of King Bleddyn of Powys. Through his mother Angharad, he was half-brother to King Gruffydd ap Llywelyn as well. Following the 1063 invasion of Wales by Harold and Tostig Godwinson that overthrew Gruffydd, Rhiwallon and Bleddyn jointly received Powys and Gwynedd on condition of faithfully serving Edward the Confessor "everywhere by water and by land". [END] 
[1]  [DOC] Tostig Godwinson ( 1026 – 25 September 1066) was an Anglo-Saxon Earl of Northumbria and brother of King Harold 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. [END]  
Answer: Northumbria
Northumbria