In 425 the Emperor Constans was assassinated by one of the Pict guards. They also attempted to kill the Emperors son, Ambrosius, but servants smuggled him to safety in Armorica among the descendants of Conans family. Vitalinus was suspected of hiring the assassination, but no proof could be found. As husband to Severa, Vitalinis was heir to the throne, and changed his name to Vortigern, meaning "High King". Sensing the growing unrest among the Britons with his kingship, he hired three ships of Saxon warriors under the leadership of Hengest and Hors for protection in 428. The people of Britain were horrified, but Vortigern told them that the Saxons had come to assist Britain in warding off an impending attack by the Irish and Picts. Their first order from the High King was to slaughter all the Pict guards that he had hired, now that he no longer needed them.
In attempt to block any interference by Agricola and the Druids, Vortigern called upon the Bishop Germanicus to investigate the suspected revival of Pelagianism in the Churches of Britain. Shortly after his arrival a large band of Welsh and Irish "barbarian" warriors staged an invasion from the west, and the former Roman general led the attack to drive them back. The cooperation of Agricola and his followers proved their loyalty to Germanicus. He returned to Gaul without any official inquiry into their religious practices.
Vortigern then became infatuated with Ronnwyn, the daughter of Hengest, and soon abandoned his Briton wife and her children. When the people of Britain became angry at the deposition of their queen, he sent for more Saxon mercenaries. With them came additional support from a neighboring tribe, the Angles. In the next few years, the Anglo-Saxon populations were granted much of the eastern coastline of the island by the High King. The Britons of those lands were forced to relocate elsewhere.
When the Grand Council of Druids met at Stonehenge at the summer solstice of 432 CE, a major topic in their discussions concerned the reign of Vortigern and the increasing presence of the Saxons and Angles on their island. These mercenaries had no respect for learning and despised both the Druids and the Christian churches. By ancient tradition, the Council of Druids made the final decision on the crowning of the kings, and that which was made had the power to be unmade. It was finally decided to remove the pretentious High King Vortigern from the throne and bestow the crown upon the head of his estranged son, Vortimer.
When this news reached London, Vortigern rallied the Saxon forces and they began an invasion against the Briton people, slaughtering men, women and children as they burned the villages and towns. Churches were torched, altars torn down and the Christian priests and bishops killed. The bloodshed spread across England and into Wales. The sons of Vortigern rallied support from all the Celtic tribes to defend their island. Prince Vortimer sent a request for help to the Roman Consul at Gaul, which was ignored.
The Celts and their Druids fought valiantly beside their Prince and finally defeated the Saxons in a battle near an old fortress of Tanatus. Those who survived fled to their ships and returned across the Channel to Saxony. Vortigern reluctantly abdicated the crown to his son. For two years he lived in the resentment of losing his throne, but his Saxon wife, Ronnwyn convinced him to make peace with his son. When the King invited them for dinner, the Saxon slipped poison into the new kings wine. With the death of Vortimer, the throne was once again claimed by Vortigern.
A great banquet was held for the coronation, and as a gesture of peace between the tribes, Vortigern ordered the seating to be arranged with Briton and Saxon nobility in alternate chairs. At a signal from Hengist the Saxons all pulled a knife from their cloaks and killed the Briton noble beside them. Hengist himself held a knife to the throat of Vortigern until he extracted a promise to return all the lands of Kent and Northumbria to Saxon control. Then Vortigern was released and Ronnwyn left with her father. The High King was left all alone and unprotected in a land turned against him.
In a short time after the Night of the Long Knives Ambrosius, son of Constans returned from his exile in Armorica. He was now well seasoned from battles in Gaul and sought revenge for the slaying of his father. With him were many Britons who had escaped the Saxon massacre, along with a warrior band of Armorica. Vortigern barricaded himself within his castle and refused to either fight or surrender. Finally the castle was set afire and Vortigern perished within.
The people of Britain then welcomed Ambrosius as the rightful heir to the throne that had been disastrously claimed by Vortigern. A descendant of Ambrosius was the famous King Arthur. This line of Briton kings led a continuous assault against the Saxons, Angles and Jutes that had claimed eastern Britain during the reign of Vortigern. With the death of Arthur, the Germanic tribes finally succeeded in conquering all of Britain, dividing it into seven kingdoms. They banned the practice of Christianity destroyed many of the ancient churches on the island. In 597 CE, Christianity was reintroduced when a bishop named Augustine (later St. Augustine) converted the King of Kent. At that time the island became known as Angleland, later changed to England.