 He also had a long-lasting friendly relationship with the Kingdom of Castile, establishing a strong alliance between realms by signing the treaties of Campillo and Ágreda in 1281 with Alfonso X of Castile and infant Sancho.With the Kingdom of Portugal, Peter established a marital alliance by which his eldest daughter Elizabeth of Aragon married Denis I of Portugal.Peter also made alliance with England, engaging his heir Alfonso III with Eleanor of England, daughter of Edward I of England.