Whilst the king was still eating, he sent for his cousin, Prince Joan, and told him in secret that, as soon as he finished his meal, he wished to leave for Vizcaya in order to kill his brother Don Tello, and that he wanted Prince Joan to go with him because he would then hand over that land to him. In spite of the fact that he was married to Doña Isabel, the sister of Don Tello's wife, the prince was very pleased to hear this and kissed the king's hands in gratitude, not suspecting in the least what the king's intentions towards him were.

The king left forthwith, accompanied by the prince, and in seven days he reached Aguilar de Campóo, where Don Tello was staying. On that day Don Tello was out hunting and, when one of his squires saw the king, he went immediately to warn his master, who fled the minute he heard this news and reached Bermeo, a town on the coast which belonged to him. He boarded a pinnace that belonged to some fishermen and headed for Bayonne, an English possession. Eager to catch Don Tello, the king followed the route he had taken.

The day that Don Tello arrived in Bermeo and took to sea was the same day that the king arrived there and boarded another boat, in the hope of catching up with him. The sea was quite rough, which made the king angry, and he stopped pursuing Don Tello, as he was a good distance ahead. The king returned to land and seized Don Tello's wife, Doña Juana.

When Prince Joan learnt that Don Tello had escaped in this way, he reminded the king of what he had said in Seville about his plans to have Don Tello killed and then hand over Vizcaya, Don Tello's land, to him. Therefore, he said, as Don Tello had fled the kingdom in exile without his permission, the king should now honour his promise and give the land of Vizcaya to him. The king replied that he would order the Vizcayans to assemble in their customary manner and that he would go there himself and command them to accept the prince as their liege lord. At this, the prince kissed both the king's hands, well pleased and full of gratitude as he was at the prospect of acquiring the land.