Cunedagius was a legendary king of the Britons, as recounted by Geoffrey of Monmouth

Geoffrey of Monmouth

Geoffrey of Monmouth was a cleric and one of the major figures in the development of British historiography and the popularity of tales of King Arthur...

. He was the son of Henwinus, Duke of Cornwall

Legendary Dukes of Cornwall

"Duke of Cornwall" appears as a title in pseudo-historical authors as Nennius and Geoffrey of Monmouth. The list is extremely patchy, and not every succession was unbroken. Indeed, Geoffrey repeatedly introduces Dukes of Cornwall only to promote them to the Kingship of the Britons and thus put an...

, and Regan, the daughter of King Leir

Leir of Britain

Leir is a legendary ancient king of the Britons, as recounted by Geoffrey of Monmouth. His story is told in a modified form by William Shakespeare in the play King Lear. In the drama, some names are identical to those of the legend Leir is a legendary ancient king of the Britons, as recounted by...

.

Cunedagius, grandson of Leir, despised the rule of his aunt Cordelia

Queen Cordelia

Queen Cordelia was a legendary Queen of the Britons, as recounted by Geoffrey of Monmouth. She was the youngest daughter of Leir and the second ruling queen of pre-Roman Britain. There is no independent historical evidence for her existence....

. With the help of his cousin Marganus

Marganus

Morganus was a legendary king of the Britons as accounted by Geoffrey of Monmouth. He was the son of Maglaurus, Duke of Albany, and Goneril, the daughter of King Leir....

, Cunedagius took over the kingdom from Cordelia and ruled half of it. Following Cordelia's suicide, Cunedagius came to rule the region of Britain southwest of the Humber

Humber

The Humber is a large tidal estuary on the east coast of Northern England. It is formed at Trent Falls, Faxfleet, by the confluence of the tidal River Ouse and the tidal River Trent. From here to the North Sea, it forms part of the boundary between the East Riding of Yorkshire on the north bank...

.

Two years after they split the island, Marganus invaded Cornwall

Cornwall

Cornwall is a unitary authority and ceremonial county of England, within the United Kingdom. It is bordered to the north and west by the Celtic Sea, to the south by the English Channel, and to the east by the county of Devon, over the River Tamar. Cornwall has a population of , and covers an area of...

 and destroyed much of the land. Cunedagius met him in battle and defeated him. Marganus fled throughout Britain until he was cornered in Wales

Wales

Wales is a country that is part of the United Kingdom and the island of Great Britain, bordered by England to its east and the Atlantic Ocean and Irish Sea to its west. It has a population of three million, and a total area of 20,779 km²...

. Cunedagius killed him and became king of all of Britain. He ruled all of Britain for 33 years and was succeeded by his son, Rivallo

Rivallo

Rivallo was a legendary king of the Britons as accounted by Geoffrey of Monmouth. He was the son of King Cunedagius and was noted as a young king who reigned frugally....

.

Geoffrey synchronizes Cunedagius' reign with the ministry of the Jewish prophet Isaiah

Isaiah

Isaiah ; Greek: ', Ēsaïās ; "Yahu is salvation") was a prophet in the 8th-century BC Kingdom of Judah.Jews and Christians consider the Book of Isaiah a part of their Biblical canon; he is the first listed of the neviim akharonim, the later prophets. Many of the New Testament teachings of Jesus...

 and the building of Rome

Rome

Rome is the capital of Italy and the country's largest and most populated city and comune, with over 2.7 million residents in . The city is located in the central-western portion of the Italian Peninsula, on the Tiber River within the Lazio region of Italy.Rome's history spans two and a half...

 by Romulus and Remus

Romulus and Remus

Romulus and Remus are Rome's twin founders in its traditional foundation myth, although the former is sometimes said to be the sole founder...

. Both events are dated to the 8th century BC

8th century BC

The 8th century BC started the first day of 800 BC and ended the last day of 701 BC.-Overview:The 8th century BC was a period of great changes in civilizations. In Egypt, the 23rd and 24th dynasties led to rule from Nubia in the 25th Dynasty...

.