Vortimer

The oldest son of Vortigern, a nefarious King of the Britons. He is known for his fierce opposition to his father's Saxon allies, as he overthrows his father and reigns as King of Britain for a brief period before his death restores Vortigern to power.
Vortimer commanded the Britons against Hengest, where the Saxons were defeated and fled to their ships, and Vortimer himself is killed. The Saxons are then re-established, assisted by other foreign Germani and pagans. Hengist then convenes his forces and sends to Vortigern an offer of peace, of which Vortigern accepts, and Hengist prepares a feast to bring together the British and Saxon leaders. The feast later becomes known as the massacre at Salisbury. 
Also: Guorthemir, Gwerthefyr, or Gwerthefyr Fendigaid: Vortimer the Blessed