Porrex I was 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 son of Gorboduc

Gorboduc

Gorboduc was a legendary king of the Britons as accounted by Geoffrey of Monmouth. He was married to Judon. At an old age, he became senile and his sons, Ferrex and Porrex, feuded over who would take over the kingdom...

 and his death began a dynastic civil war.

In the final years of Gorboduc's life, Porrex waged war with his brother, Ferrex

Ferrex

Ferrex was a legendary king of the Britons as accounted by Geoffrey of Monmouth. He was the son of Gorboduc and Judon.When his father had become old, he waged war on his brother, Porrex, for who would succeed to the kingship. He fled to Gaul and enlisted the help of Suhard, the king of the...

. He planned to ambush his brother but his brother fled to Gaul

Gaul

Gaul was a region of Western Europe during the Iron Age and Roman era, encompassing present day France, Luxembourg and Belgium, most of Switzerland, the western part of Northern Italy, as well as the parts of the Netherlands and Germany on the left bank of the Rhine. The Gauls were the speakers of...

 to enlist the aide of Suhard, the king of the Franks

Franks

The Franks were a confederation of Germanic tribes first attested in the third century AD as living north and east of the Lower Rhine River. From the third to fifth centuries some Franks raided Roman territory while other Franks joined the Roman troops in Gaul. Only the Salian Franks formed a...

. When Ferrex returned with a large Gaulish army, Porrex attacked and Ferrex and the army were defeated. Some time after, his mother, Judon, avenged Porrex's murder of Ferrex and hacked him to pieces in his sleep. His death sparked a civil war which would not be resolved until the reign of Dunvallo Molmutius

Dunvallo Molmutius

Dunvallo Molmutius was a legendary king of the Britons as accounted by Geoffrey of Monmouth. He was the son of Cloten, the King of Cornwall, and he restored order after the "Civil War of the Five Kings"...

. His death shifted the dominant genealogical

Genealogy

Genealogy is the study of families and the tracing of their lineages and history. Genealogists use oral traditions, historical records, genetic analysis, and other records to obtain information about a family and to demonstrate kinship and pedigrees of its members...

 royal house of Brutus to another house, 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...

.