In 1356, when King Pedro of Castile had been on the throne for almost seven years, while in Seville he ordered a galley to be equipped for a leisure trip to go and view the tunny-fishing grounds. He sailed to Sanlúcar de Barrameda and saw, there in the harbour, ten Catalan galleys and one large vessel the captain of which was an Aragonese knight named Messer Francesc del Perelló. The ships were going to support the King of France against the King of England, by order of the King of Aragon.

When the captain came into port to take on supplies he found two vessels from Piacenza, loaded with oils, bound for Alexandria, whereupon he seized them, declaring that they were the property of the Genoese, with whom the Catalans were at war at the time. The king sent word to him to say that, since these vessels were in a port which belonged to his kingdom, he was not to seize them, at least out of respect for the king's presence. The captain replied that those people were enemies of the King of Aragon and therefore he had every right to do so. The king sent word to him a second time, saying that, if he did not relinquish them, he would have all the Catalan merchants who were in Seville put in prison there and all their possessions confiscated.

In spite of all this, the commander of the galleys did not wish to obey the king's instructions and sold the vessels there and then for 700 doblas. He then went on his way without another word to the king. The king was greatly displeased by this and with good reason, but the vengeance he wrought was out of all proportion, for, just as a tiny spark can start a huge fire if the right materials are to hand, so it was that, simply to take his revenge on Aragon for this incident, King Pedro, mad with rage, instigated a cruel and bloody war against Aragon, which was to last for many years, as you will hear presently.

First of all, he ordered all the Catalan merchants who were in Seville to be seized and all their possessions confiscated. The following day, he made a swift departure from the city by land, put all the Catalan merchants in chains and then sold off everything they had.