Considered to be one of the founding peoples of the north, the Strathclyde Britons were of Celtic descent and were divided into three sub-kingdoms. The Selgovae dwelled north of the Clyde, while the Novantii lived in Galloway in the southwest of Scotland. The Rhiged lived in what later became the counties of Cumberland, Westmorland, and Lancashire in England.
The lands of the Strathclyde Britons were constantly beset by invaders from all directions. Gaels assailed their territory from Ireland in the west. Attempting to protect their colony in the south, the Roman Empire launched a military campaign under Julius Agricola around 78 A.D. During the 5th century, the Angles invaded from the east. The Picts and Dalriadans followed, overrunning the lands from the north, and the Vikings extended their influence into the borderlands, attempting coastal landings from the Isle of Man. The kingdom of Strathclyde, which flourished from the 7th to 10th centuries, was extinguished when King Cnut of Denmark conquered Cumberland during the early 11th century.
Nevertheless, the Strathclyde Britons thrived in the face of these threats. Despite the lawlessness of the borderlands, where horse thievery and cattle raids were a common part of life, they came to live in relative peace with their eastern neighbors, the Boernicians, with whom they shared a common way of life. The Strathclyde Britons were unaffected by the artificial line that demarcated the Scottish/English border and generally didn't suffer from the dissolution of the Border Clans as they were more loyalty to their own clans than to either the Scottish or English crowns.