Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. The Night of the Long Knives is the name Geoffrey of Monmouth gave to the (possibly apocryphal) treacherous killing of native British chieftains by Anglo-Saxon mercenaries on Salisbury Plain in the 5th century. The event came to be known as Brad y Cyllyll Hirion (The Treachery of the Long Knives") in Welsh, and became a prominent symbol of Saxon treachery. According to the tradition, Vortigern, who has become the high king of the Britons in the wake of the Roman withdrawal from Britain, allows Anglo-Saxons under Hengist and Horsa to settle on the Isle of Thanet. He offers them additional provisions in exchange for their service as mercenaries against incursions by Picts and Scots. The settlers, however, manipulate Vortigern into allowing them to increase their numbers and granting them more land, eventually including all of Kent. "