Henry was the third child of King John I of Portugal, founder of the Aviz dynasty, and of Philippa of Lancaster, John of Gaunt's daughter. Henry encouraged his father to conquer Ceuta (1415), the Muslim port on the North African coast across the Straits of Gibraltar from the Iberian peninsula. He learnt of the opportunities from the Saharan trade routes that terminated there, and became fascinated with Africa in general; he was most intrigued by the Christian legend of Prester John and the expansion of Portuguese trade. Henry is regarded as the patron of Portuguese exploration.