 Complete the following phrase:  Álvares served as chamberlain and secretary of the Portuguese royal prince or infante the holy Ferdid, the youngest of the Illustrious Generation   the children of King John I and Philippa of Lancaster. He accompanied Ferdid on the ill-fated Portuguese campaign to conquer Tangier from Marinid Morocco in 1437. To preserve his army from destruction, Prince Henry the Navigator, commander of the expedition, signed a treaty that agreed to deliver Ceuta 