March 18, 978: Death of King Edward the Martyr
When King Edgar the Peacemaker died in 975, he left sons by different mothers. The younger son, Æthelred, became king in 978 and for nearly forty years tried to save the country from the Vikings, a long fight whose failure led to the nickname "the Unready". The older son, Edward, became king in 975, but was killed at Corfe on March 18, 978; he was almost immediately celebrated as a saint and martyr, and his half-brother declared that St Edward's festival should be celebrated all over England.
We don't know who killed Edward. The Anglo-Saxon Chronicle states that he was killed at Corfe on the evening of 18 March, and buried without royal honours, and that "no worse deed was ever done since first the English came to Britain".
Other sources placed the blame more squarely on the beneficiaries of the crime, Æthelred and his mother Ælfthryth. The near-contemporary Life of St Oswald notes that certain zealous thegns (minor nobles) of Æthelred surrounded and killed Edward when Edward had come to visit his half-brother, while a later source adds that it was Ælfthryth's plot from the beginning, so that her son might be king. Still later legend turns Ælfthryth into the wicked stepmother par excellence, dabbling in magic and torturing abbots with hot irons.
At this distance, the death remains a mystery. There was civil unrest in the years after Edgar's death, and it is quite likely that supporters of Æthelred thought that killing Edward would bring them their lord's favour, whether or not he explicitly said "Will no one rid me of this troublesome half-brother" (to paraphrase Henry II's famous death-warrant for Thomas a Becket). (For a fictional treatment of a similar situation, see The Lions of Al-Rassan by Guy Gavriel Kay.)
Review the history, 975-9.