Who was perhaps not the only king of the West Saxons at the time, whos viceroy is said to have constructed Chisbury Camp, and to have founded Abingdon Abbey?
Cissa (West Saxon) Cissa was reported as the viceroy of king Centwine of Wessex (reigned c.676-686). Cissa is sometimes said to have himself been a king of Wessex, but does not feature in the king lists or genealogies. He is said to have constructed Chisbury Camp, and to have founded Abingdon Abbey.
Guiderius Guiderius (Welsh Gwydr) is a legendary British king according to Geoffrey of Monmouth's "Historia Regum Britanniae" ("History of the Kings of Britain") and related texts. He can probably be identified as deriving from the historical Togodumnus.