Eventually, the two reached a peaceful accord after mediation by Juan del Campo, Bishop of Oviedo; this secured Constanza's release from prison.

The public humiliation of his daughter led Afonso IV to have his son and heir, Peter I of Portugal, marry the no less aggrieved Castilian infanta, Constanza.

A year after the peace treaty was signed in Seville, Portuguese troops played an important role in defeating the Moors at the Battle of Río Salado in October 1340.

Political intrigue marked the last part of Afonso IV's reign, although Castille was torn by civil war after Alfonso XI died.

Inês was the daughter of an important noble family from Galicia, with links (albeit illegitimate) to both the royal houses of Castile and Portugal.

Worried about his legitimate grandson's life, and the growing power of Castile within Portugal's borders, Afonso ordered Inês de Castro first imprisoned in his mother's old convent in Coimbra, and then murdered in 1355.

He expected his son to give in and marry a princess, but Peter became enraged upon learning of his wife's decapitation in front of their young children.

The conflict with Pedro, and the explorations he initiated, eventually became the foundation of the Portuguese national epic, Os Lusíadas by Luís de Camões.