Constantine the Great, Roman and Briton Emperor
From Bononia, Germania Constantine and his brother crossed the Channel to Britain and made their way to Eboracum (York), capital of the province of Britannia Secunda and home to a large military base. Constantine was able to spend a year in northern Britain at his father’s side, campaigning against the Picts beyond Hadrian’s Wall in the summer and autumn.
Constantius’s campaign, like that of Septimius Severus before it, probably advanced far into the north without achieving great success. Constantius had become severely sick over the course of his reign, and died on 25 July 306 in Eboracum (York). Before dying, he declared his support for raising Constantine to the rank of full Augustus. The Alamannic king Chrocus, a barbarian taken into service under Constantius, then proclaimed Constantine as Augustus. The troops loyal to Constantius’ memory followed him in acclamation. Gaul and Britain quickly accepted his rule;Iberia, which had been in his father’s domain for less than a year, rejected it.
Geoffrey of Monmouth’s Historia
Because of his fame and his being proclaimed Emperor in the territory of Roman Britain, later Britons regarded Constantine as a king of their own people. In the 12th century Henry of Huntingdon included a passage in his Historia Anglorum that Constantine’s mother Helena was a Briton, the daughter of King Cole of Colchester. Geoffrey of Monmouth expanded this story in his highly fictionalized Historia Regum Britanniae, and account of the supposed Kings of Britain from their Trojan origins to the Anglo-Saxon invasion. According to Geoffrey, Cole was King of the Britons when Constantius, here a senator, came to Britain. Afraid of the Romans, Cole submitted to Roman law so long as he retained his kingship. However, he died only a month later, and Constantius took the throne himself, marrying Cole’s daughter Helena. They had their son Constantine, who succeeded his father as King of Britain before becoming Roman Emperor.
Historically, this series of events is extremely improbable. Constantius had already left Helena by the time he left for Britain.Additionally, no earlier source mentions that Helena was born in Britain, let alone that she was a princess. Henry’s source for the story is unknown, though it may have been a lost hagiography of Helena.
St. Helen’s Church location in York, UK.