After the duke enjoyed being for a few days with the king and his daughter, he embarked to travel with his men, who were very few: they were all accommodated very adequately in six galleys, and the rest of the galleys accompanied them as an honour to the duke. This was at the end of September. When they had left the harbour and reached the open sea, God gave them such a good voyage that in a few days they arrived in Gascony at the afore-mentioned town of Bayonne, under English rule.

When the King of Castile learned that the duke was in that place, he decided to send him his ambassadors to sign that treaty of which we have already made mention. Those whom the king appointed to go there were Friar Fernando de Illescas of the Order of Saint Francis, who was his confessor; Pero Sánchez de Castilla, a doctor of laws; and Doctor Álvaro Martínez, all of whom had originally gone with the other envoys to speak with the duke. As all that was necessary had already been said regarding this matter in the agreements that had been reached in the town of Trancoso, there was no need for a long delay; there was nothing else to do except to conclude the treaty so that it would be valid. Omitting many clauses that were included in it, here we will tell only of those that pertain to the king's demand and nothing else. These stated that:

The King of Castile and the Duke of Lancaster and his wife the duchess should do everything in their power to have Prince Enrique, the first-born son of the King of Castile, betrothed to Lady Catalina, the daughter of the duke; within two months of the swearing and signing of this treaty, this betrothal should be celebrated publicly according to the rites of the Church, and should be followed by marriage as soon as possible.

Likewise, Prince Fernando, the second son of the King of Castile, should neither be betrothed nor take a wife until the aforementioned prince, his brother, reached fourteen years of age (for he was nine at the time, and this was so that he would be able to give legal consent to his betrothal and consummate the marriage), and of this, Prince Fernando should swear an oath.