 In March 978 , King Eadweard was assassinated at Corfe Castle , possibly at the instigation of his stepmother , and Æthelred the Unready became king . His coronation on Low Sunday 31 March 978 , was the last state event in which Dunstan took part . When the young king took the usual oath to govern well , Dunstan addressed him in solemn warning . He criticised the violent act whereby he became king and prophesied the misfortunes that were shortly to fall on the kingdom , but Dunstan 's influence at court was ended . Dunstan retired to Canterbury , to teach at the cathedral school . 
