Carausius, originally a Menapian pilot, but promoted to the command of a Roman fleet, made common cause with his fellow-citizens, and proclaimed himself emperor of Great Britain, where the naval superiority of the Menapians left him no fear of a competitor.

In recompense of the assistance given him by the Franks, he crossed the sea again from his new empire, to aid them in their war with the Batavians, the allies of Rome; and having seized on their islands, and massacred nearly the whole of its inhabitants, he there established his faithful friends the Salians.

Constantius and his son Constantine the Great vainly strove, even after the death of the brave Carausius, to regain possession of the country; but they were forced to leave the new inhabitants in quiet possession of their conquest..