The: Angles, Saxons and Jutes invaded Britain after the Romans left.
They came across the North Sea in wooden boats from what is now: Germany, Denmark and the Netherlands.
Their land often flooded and it was difficult to grow crops, so they were looking for new places to farm.
Some Britons invited them to keep out invaders from Scotland and Ireland, offering them money in return.
Other people like King Arthur tried to fight them off however, but they soon settled in what we now call England (meaning 'Angle Land').
Those that didn't like the Anglo-Saxons fled westward and went to live in Wales and Cornwall.