Vortigern is impressed by the equivocal nature of Merlin’s prophecies and his unusual willingness to speak his mind. Vortigern wants to know his fate and asks Merlin to divine it. Merlin responds that Vortigern made a mistake when he betrayed Aurelius Ambrosius and Utherpendragon’s father. They are preparing an assault of Britain, and Vortigern is in danger by both sides since the Saxons also want to destroy him. Merlin predicts that Hengist will be killed and Aurelius Ambrosius crowned king. Vortigern’s descendants will poison him, but they will be destroyed by the Boar of Cornwall mentioned in Merlin’s prophecies.

The following day, Aurelius Ambrosius lands in Britain. The previously scattered Britons gather, and the clergy anoint Aurelius Ambrosius as king. The Britons want to attack the Saxons, but Aurelius Ambrosius is intent on first avenging his father and brother. He gives a speech enumerating Vortigern’s betrayals of Britain and urges his soldiers to take vengeance against Vortigern. They comply, burning down Vortigern’s tower with him in it. Hengist and the Saxons hear the news and are frightened because of Aurelius Ambrosius’ nobility, piety, and skill in battle. The Saxons retreat and fortify their castles and towns near Scotland, which “never missed an opportunity of making matters worse whenever the Britons were in distress” (160).