Danelaw

When the Vikings invaded the east coast of England in the late 800s, their conquests reached as far as the southern kingdom of Wessex, where they were halted by the army of Alfred the Great. The invaders, many of whom were Danish, retreated back north and east to the lands they had conquered, and settled there. This region - stretching from Essex, just above London, through East Anglia and the eastern Midlands, all the way up to Northumbria - was distinguished from the surrounding territory by its unique legal practices, which, because they were decidedly Danish in influence, made up what Old English folks down south called the Dena lagu or, in today's English, the "Danes' law." Historians later applied the term Danelaw not only to the legal system of the region but to that geographical area itself.