Trahern () is a legendary

King of the Britons The title King of the Britons ( cy, Brenin y Brythoniaid, la, Rex Britannorum) was used (often retrospectively) to refer to the most powerful ruler among the Celtic Britons, both before and after the period of Roman Britain up until the Norma ...

Geoffrey of Monmouth Geoffrey of Monmouth ( la, Galfridus Monemutensis, Galfridus Arturus, cy, Gruffudd ap Arthur, Sieffre o Fynwy; 1095 – 1155) was a British cleric from Monmouth, Wales and one of the major figures in the development of British historiograph ...

's fictional ''

Historia Regum Britanniae ''Historia regum Britanniae'' (''The History of the Kings of Britain''), originally called ''De gestis Britonum'' (''On the Deeds of the Britons''), is a pseudohistorical account of British history, written around 1136 by Geoffrey of Monmouth. I ...

''. According to Geoffrey, Trahern was king of the

Britons British people or Britons, also known colloquially as Brits, are the citizens of the United Kingdom of Great Britain and Northern Ireland, the British Overseas Territories, and the Crown dependencies.: British nationality law governs mo ...

and

Roman Roman or Romans most often refers to: *Rome, the capital city of Italy *Ancient Rome, Roman civilization from 8th century BC to 5th century AD *Roman people, the people of ancient Rome *''Epistle to the Romans'', shortened to ''Romans'', a letter ...

senator. He was the brother of the late King

Coel Coel ( Old Welsh: ''Coil''), also called ''Coel Hen'' (Coel the Old) and King Cole, is a figure prominent in Welsh literature and legend since the Middle Ages. Early Welsh tradition knew of a Coel Hen, a 4th-century leader in Roman or Sub-Rom ...

and was sent by Emperor

Constantine I Constantine I ( , ; la, Flavius Valerius Constantinus, ; ; 27 February 22 May 337), also known as Constantine the Great, was Roman emperor from AD 306 to 337, the first one to Constantine the Great and Christianity, convert to Christiani ...

to restore

Britain Britain most often refers to: * The United Kingdom, a sovereign state in Europe comprising the island of Great Britain, the north-eastern part of the island of Ireland and many smaller islands * Great Britain, the largest island in the United King ...

to Roman rule during the usurpation of Octavius (

Eudaf Eudaf Hen (Eudaf "the Old") is a figure of Welsh tradition. He is remembered as a King of the Britons and the father of Elen Luyddog and Conan Meriadoc in sources such as the Welsh prose tale '' The Dream of Macsen Wledig'' and Geoffrey of Monmou ...

). When Octavius took control of Britain from Rome, Constantine sent three

Roman legion The Roman legion ( la, legiō, ) was the largest military unit of the Roman army, composed of 5,200 infantry and 300 equites (cavalry) in the period of the Roman Republic (509 BC–27 BC) and of 5,600 infantry and 200 auxilia in the period of ...

s to Britain under the command of Trahern. He landed at 'Kaerperis' and captured it forcing Octavius to conscript all the island into the army to combat the Roman legions. Octavius met Trahern in a field outside

Winchester Winchester is a City status in the United Kingdom, cathedral city in Hampshire, England. The city lies at the heart of the wider City of Winchester, a local government Districts of England, district, at the western end of the South Downs Nation ...

where they fought and Octavius won. Trahern fled to

Alba ''Alba'' ( , ) is the Scottish Gaelic name for Scotland. It is also, in English language historiography, used to refer to the polity of Picts and Scottish people, Scots united in the ninth century as the Kingdom of Alba, until it developed i ...

ny and pillaged the land. That caused Octavius to react again, where he met Trahern in

Westmorland Westmorland (, formerly also spelt ''Westmoreland'';R. Wilkinson The British Isles, Sheet The British IslesVision of Britain/ref> is a historic county in North West England spanning the southern Lake District and the northern Dales. It had an ...

, but Octavius was defeated this time. Octavius fled Britain and Trahern took on the crown himself. A few years later, supporters of Octavius, who was in exile in

Norway Norway, officially the Kingdom of Norway, is a Nordic country in Northern Europe, the mainland territory of which comprises the western and northernmost portion of the Scandinavian Peninsula. The remote Arctic island of Jan Mayen and t ...

, attacked Trahern in a forest. They killed him and Octavius immediately returned and was recrowned king.

References

{{Geoffrey of Monmouth British traditional history