Osbeorn Bulax's father governed on what king's behalf?
Osbeorn Bulax Osbeorn (died c. 1054), given the nickname Bulax, was the son of Siward, Earl of Northumbria (died 1055). He is one of two known sons — probably the older — of Siward. While it is normally assumed he was the son of Siward's Bamburgh wife Ælfflæd, it has been suggested by William Kapelle that Osbeorn's mother was not Ælfflæd. The nickname "Bulax" probably represents the Old Norse term for "Poleaxe".
Ecgfrith of Mercia Ecgfrith was king of Mercia from 29 July to December 796. He was the son of Offa, one of the most powerful kings of Mercia, and Cynethryth. In 787, Ecgfrith had been consecrated king, the first known consecration of an English king, probably arranged by Offa in imitation of the consecration of Charlemagne's sons by the pope in 781.