Among the places in the Alentejo that maintained support for Castile was the town of Portel, the governor of which was a great Portuguese nobleman called Fernão Gonçalves de Sousa, married to Dona Teresa de Meira, who had been governess to Beatriz, the Queen of Castile. It is said that, owing to his wife's counsel, he declared against Portugal and became a Castilian, as did Gonçalo Vasques de Azevedo and others.

As well as the people that he had with him, there were in the town as Officer of the Marches, Don García Fernández, the Lord of Villagarcía, who later became Master of the Order of Santiago, with 120 lances and other Castilians. The town thus being for Castile, Fernão Gonçalves, for fear of its inhabitants, impounded the weapons of all of them and placed them in the castle. It happened one day that men from Évora attacked Portel and carried off a number of cattle and prisoners. García Fernández went out to them with a company of troops as well as men from the town, but the latter had nothing to take along except capes over their arms and stones in their hands.

When García Fernández saw that, he took them for honourable men and said to Fernão Gonçalves that he did not think it right that they should be weaponless in that way; because, even though they might wish to carry out some worthy action, they did not have the wherewithal, and they cut very poor figures going with him with capes over their arms and stones in their hands. On account of these and other words that he spoke on the matter, Fernão Gonçalves was moved to return their weapons to them.

In this town of Portel was a priest called João Mateus, who very much wished that the town should support Portugal and declare for the Master. He considered in his heart that this could readily be done by having keys counterfeited in order to open the gates at a time of his choosing. So he took wax and inserted it in the locks, and went secretly to Évora where Nuno Álvares was.