But Vortigern above all the rest both admired and applauded the wisdom, and prophetical spirit of the young man: for that age had produced none that ever talked in such a manner before him. Being therefore curious to learn his own fate, he desired the young man to tell him what he knew concerning that particular. Merlin answered:-- "Fly the fire of the sons of Constantine, if you are able to do it: already are they fitting out their ships: already are they leaving the Armorican shore: already are they spreading out their sails to the wind. They will steer towards Britain: they will invade the Saxon nation: they will subdue that wicked people; but they will first burn you being shut up in a tower. To your own ruin did you prove a traitor to their father, and invite the Saxons into the island. You invited them for your safeguard; but they came for a punishment to you. Two deaths instantly threaten you; nor is it easy to determine, which you can best avoid. For on the one hand the Saxons shall lay waste your country, and endeavour to kill you: on the other shall arrive the two brothers, Aurelius Ambrosius and Uther Pendragon, whose business will be to revenge their father's murder upon you. Seek out some refuge if you can: to-morrow they will be on the shore of Totness. The faces of the Saxons shall look red with blood, Hengist shall be killed, and Aurelius Ambrosius shall be crowned. He shall bring peace to the nation; he shall restore the churches; but shall die of poison. His brother Uther Pendragon shall succeed him, whose days also shall be cut short by poison. There shall be present at the commission of this treason your own issue, whom the boar of Cornwall shall devour." Accordingly the next day early, arrived Aurelius Ambrosius and his brother, with ten thousand men.

Geoffrey of Monmouth's Historia Regum Britanniae