According to William of Worcester, writing in the fifteenth century, Cadoc was a survivor of the Cornish royal line at the time of the Norman Conquest of England in 1066 and was appointed as the first Earl of Cornwall by William the Conqueror. William Worcester (c 1415 &ndash c 1482 English chronicler was a son of William of Worcester, a Bristol citizen and is sometimes called William The Kingdom of Cornwall or Kernow existed during the sub-Roman and Early Middle Ages in Great Britain 's south-western peninsula The title of Earl of Cornwall was created several times in the Peerage of England before 1337, when it was superseded by the title Duke of Cornwall William I of England ( 1027 His reign which brought Norman culture to England had an enormous impact on the subsequent course of England in the Middle Ages His date of death is not known, but a prince named Hywel of Cornwall (who is likely to have come from Cornouaille in western Brittany but may have descended from the line of Cornwall in Britain and is described as Count of Cornwall) inherited the throne of Brittany through marriage to Havise, heiress of Brittany in 1066. Hoel II of Cornwall (bc 1031 d 1084 was count of Kernev ( French: Cornouaille, Breton: Kernev) from 1058 as Hoel V and after Cornouaille is an historic region in Brittany, in northwest France. The Kingdom of Cornwall or Kernow existed during the sub-Roman and Early Middle Ages in Great Britain 's south-western peninsula Brittany (Breizh bʁejs Bretagne; Gallo: Bertaèyn) is a former independent Celtic kingdom and Duchy, now incorporated into He ruled Brittany alone from 1072, dying in 1084. He was succeeded by his son and then his grandson. His last descendant, a great-grandson also called Hoël, died disinherited in 1156. There were two other patrilineal descendants of this line whose children are not recorded which allows for the possibility that the line endured (see Kings and dukes of Brittany family tree). Patrilineality (aka agnatic kinship) is a system in which one belongs to one's father's lineage it generally involves the Inheritance of property names or titles This is a family tree of the Dukes of Brittany from the 9th century, to the annexation of Brittany by France in 1532.