Having determined the day on which the town would be seized, the king discussed the matter with a number of his noblemen, telling them to take the horses which were least likely to neigh. He took with him 300 horsemen, but only a very few foot soldiers. He attended mass and dined early, and they left lightly equipped, without mules or other encumbrances. At dead of night they reached the flat plain of São Redanhas, just half a league away from the small village where Afonso Lourenço was waiting for them. From there he led them round to the valley with a grove known as Santa Maria, where the trees are very dense and which lies about three crossbow shots away from the town. Once there, each man did what he could to prevent his horse from neighing, and, when one of the horses did neigh, the king immediately had it killed. On the day when the king set off, the order was given to detain everyone travelling the roads to or from Oporto, lest any of them should divulge the news [of their advance].

Now, whenever Afonso Lourenço set out from Guimarães, Paio Rodrigues, who remained in the town, dealt with whatever was needed inside it. It came about that, on the day when Afonso Lourenço left, he had a word with João Azedo, the man who held the keys of the postern gate. Afonso Lourenço said to him that, since he worked alone and was intending to bring in a cart laden with a large vat, he was asking him to open the gate at a very early hour, so that no one should see him. The gatekeeper, who knew nothing about the plan, said that he would be happy to do so. Later on, Paio Rodrigues requested the gatekeeper to go and see whether his brother[-in-law] was on his way, and so João Azedo kept his promise and opened the gate very early. Once it was open, Paio Rodrigues and his men detained the gatekeeper. Paio Rodrigues then kept very quiet, deployed men to guard the gate and posted others on the ramparts to forestall and hold back any forces which might seek to rush to the gate.