On the constable's advice the king decided to go to Oporto, intending to capture several places in the Minho area which had declared for the King of Castile. Before he left Coimbra, since he was somewhat suspicious of Gonçalo Mendes de Vasconcelos, especially as he was a relative of Queen Leonor, he deemed it appropriate to take the Coimbra castle from him and entrust it to someone on whom he could rely. He spoke with Vasco Martins de Melo and told him, when he saw him outside the castle, to go in and take it over. Vasco Martins did so, and, though Gonçalo Mendes was aggrieved, the king was able to please and pacify him by granting him other favours. Neither of his sons, Mem Rodrigues and Rui Mendes, who had been accompanying the king for some time, was greatly troubled by this, because they had been apprehensive that their father might use the castle to do something for which they could be blamed. Then the king entrusted the castle to Lopo Vasques de Sequeira, a man who later became grand commander of the Order of Avis and remained in charge of the castle for the rest of his days.

While the king was handling this matter, a message reached him from Lisbon to say that most of the King of Castile's fleet was standing off the city and that very soon the rest would arrive. The king conveyed this message to the constable and discussed with him the best way to approach the matter. The constable, in his great anxiety to serve him, answered that, if he would graciously grant him permission and a suitable number of his troops, then with them and those that he already had, he would serve him by going to do battle with the [Castilian] fleet. The king replied that he was most grateful to him, for that indeed was his wish, even though he had not mentioned it to him yet. He then gave him a message for the city of Oporto, and the constable left at once to arrange his departure. When he arrived there, he met his wife and daughter, Dona Beatriz (who later became a countess), who had just arrived from Guimarães, where they had been detained for a time, as the town had declared for Castile.