Germanic raiders who became known collectively as ‘Saxons’ had been attacking England since the 3rd century, but after the Romans left at the beginning of the 5th century, one of the Britons’ leaders, named Vortigern, had the bright idea of hiring Saxons as mercenaries to fight the Picts and Scots who had been raiding northern England.
So in 449, the brothers Hengest and Horsa arrived in Kent. They were very successful against the Picts and Scots, but when the Britons tried to defy their increasing demands for land, the Saxons fought and heavily defeated their employers, perhaps at Aylesford in Kent in 455.
Two years later, the Britons suffered an even more decisive defeat, perhaps at Crayford. They are said to have lost 4,000 killed, while the survivors ‘fled to London in great terror’.
In the late fifth or early sixth century, the Britons had a series of successes, perhaps under King Arthur, but the year 577 saw another crushing defeat at Dyrham, near Bath, where three British kings were killed, and by 600 most of what had been Roman Britain was in Saxon hands.
*This is an interview with me on British Forces Broadcasting about my new book – Britain’s 20 Worst Military Disasters