It was certain, as indeed the King of Castile was informed, that King Fernando was making an alliance against him with the English, despite the agreements and treaties which existed between them, as you have already heard. In fact, the Duke of Lancaster had sent his emissaries shortly beforehand to King Fernando; the duke was the second son of the King of England and called himself the King of Castile on the grounds that his wife, Princess Constanza, was the daughter of King Pedro, as we have said.

The emissaries were the knight Juan Fernández Andeiro and Roger Hore, who was the duke's squire. They arrived in July near Braga, where the King of Portugal then was, and having shown their authorization to carry out the task, they drew up the following agreement:

The king and the duke were henceforth always to be true friends and would help each other on land and sea against King Enrique, who called himself King of Castile, and against King Pedro of Aragon, so that, if the duke arrived to make war on King Enrique or on the King of Aragon, and, having entered the kingdom of Navarre, were to begin to make war on either of them by deploying the troops which he brought with him, then King Fernando would be bound to wage war on them at once. If the duke were to enter either of the aforesaid kingdoms with his forces, then the King of Portugal would be bound to enter with his forces from the opposite direction. This assistance and the warfare involved would be at the expense of each of them. Anything that King Fernando were to capture in the kingdom of Castile, except for towns or castles or land, he could regard as his own without further contention. Anything captured from the kingdom of Aragon would belong to whosoever seized it.

These clauses about the war and the assistance they undertook to give each other (and other clauses, which for brevity's sake we shall omit) were then signed by the king and the Duke of Lancaster. The title of the duke (as he then was called) was set out as follows: ‘Don Juan, by the grace of God King of Castile, León, Toledo, Galicia, Seville, Córdoba, Murcia, Jaén, the Algarve and Algeciras, Duke of Lancaster and Lord of Molina.’