http://en.wikipedia.org/wiki/Ethelred_II

Ethelred II , also known as Æthelred II, Aethelred II, Ethelred the Unready, Æthelred the Unready and Aethelred the Unready , was King of England . He was a son of King Edgar and his queen Ælfthryth. The majority of his reign was marked by a developing, defensive war against Danish invaders.