蘭開斯特公爵
John of Gaunt, 1st Duke of Lancaster, also had, since 1371, claims to the Castilian throne, and saw in this deal a means of enforcement of this cause. In June, the Duke of Lancaster sent an English army (composed by the famous English archers) under the command of the Earl of Cambridge to Lisbon in support of the Portuguese troops in an incursion into the Castilian territory.