Ingenius is a legendary king of the Britons as accounted 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 fourth son of King Morvidus

Morvidus

Morvidus was a legendary king of the Britons from 341 to 336 B.C., as recounted by Geoffrey of Monmouth. He was the illegitimate son of Danius by his mistress Tanguesteaia....

 and brother of Gorbonianus

Gorbonianus

Gorbonianus was a legendary king of the Britons as accounted by Geoffrey of Monmouth. He was the eldest son of King Morvidus, and the brother of Archgallo, Elidurus, Ingenius, and Peredurus, and...

, Archgallo

Archgallo

Archgallo was a legendary king of the Britons as accounted by Geoffrey of Monmouth. He was the second son of King Morvidus and brother of Gorbonianus....

, Elidurus

Elidurus

Elidurus the Dutiful was a legendary king of the Britons as accounted by Geoffrey of Monmouth. He was the third son of King Morvidus and brother of Gorbonianus, Archgallo, Ingenius, and Peredurus....

, and Peredurus

Peredurus

Peredurus is a legendary king of the Britons in Geoffrey of Monmouth's pseudohistorical chronicle Historia Regum Britanniae. According to Geoffrey he was the youngest son of King Morvidus and brother of Gorbonianus, Archgallo, Elidurus, and Ingenius....

.

Following the return of Elidurus to the kingship of Britain

British Iron Age

The British Iron Age is a conventional name used in the archaeology of Great Britain, referring to the prehistoric and protohistoric phases of the Iron-Age culture of the main island and the smaller islands, typically excluding prehistoric Ireland, and which had an independent Iron Age culture of...

, Ingenius joined with his brother Peredurus and attacked their older brother. They succeeded in capturing him and locked him in a guarded tower in Trinovantum

Trinovantum

Trinovantum, in medieval British legend, is the name given to London in earliest times. According to Geoffrey of Monmouth's Historia Regum Britanniae it was founded by the exiled Trojan Brutus, who called it Troia Nova , which gradually corrupted to Trinovantum...

. Instead of fighting over who ruled the island, they split the island giving 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...

 to Ingenius and Alba

Alba

Alba is the Scottish Gaelic name for Scotland. It is cognate to Alba in Irish and Nalbin in Manx, the two other Goidelic Insular Celtic languages, as well as similar words in the Brythonic Insular Celtic languages of Cornish and Welsh also meaning Scotland.- Etymology :The term first appears in...

ny to Peredurus. He ruled his portion of the island for seven years then died, giving the whole of the island to his brother, Peredurus. His son Idvallo

Idvallo

Idvallo was a legendary king of the Britons as accounted by Geoffrey of Monmouth. He was the son of King Ingenius and he replaced King Enniaunus. Idvallo is said by Geoffrey to have reigned righteously to mend the ills his cousin had brought. He was succeeded by his cousin Runo....

 would later become king of Britain.