While the King of Portugal was in Guimarães, rejoicing at the good news about the battle [at Trancoso], he received a reliable message which reported that the King of Castile, together with a very large force that he had assembled, was rapidly getting ready to invade Portugal via Badajoz. Furthermore, all his fleet was already at Lisbon, the city was under siege from the sea and the river was blockaded, with the result that the citizens of Lisbon could not use it. That was because the city was under surveillance by 40 great naos, 12 barges and 10 galleys, as well as 3 lenhatos and five small boats which were laden with supplies.

Perturbed by this news, the King of Portugal discussed the entire matter with the constable. The constable, who had sought many ways in which he could fight against the King of Castile but had never had the opportunity, realised that the time was now ripe for him to achieve this. After they had first debated the question at length, they both came to the conclusion that the best way to proceed, in order to hinder these actions was, with God's help, to launch an attack on the King of Castile, despite the immense forces which he was reported to be bringing with him.

Having ensured due protection and equipment both for those towns which they had captured and for those in that region which had gone over to him, the king left at once for Oporto, intending to assemble his army and to await the King of Castile wheresoever he happened to confront him. From Oporto he made his way to Coimbra. While he was there, a knight arrived from the King of Navarre, in secret and dressed as a man of little importance, so as not to be recognised. By him the King of Navarre had sent a message to say that he wished to be the friend of the King of Portugal against the King of Castile and to wage war against him from his own kingdom while the King of Castile was in Portugal. He requested the King of Portugal to act in a similar fashion, should the King of Castile make war on Navarre, and urged that they be friends against their common foe. further action was taken on the matter, there is no point in dwelling on it.