Philippa provided royal patronage for English commercial interests that sought to meet the Portuguese desire for cod and cloth in return for wine, cork, salt, and oil shipped through the English warehouses at Porto. Her eldest son, Duarte, authored moral works and became king in 1433; Pedro, who travelled widely and had an interest in history, became regent (1439-1448) after Duarte died of the plague in 1438; Ferdinand the Saint Prince (1402-1443), who became a crusader, participated in the attack on Tangiers in 1437; and Henrique – also known as Prince Henry the Navigator (1394-1460) – became the master of the Order of Christ and the instigator and organiser of Portugal's early voyages of discovery.