King John I assembled his fleet in the harbour of Lagos, before setting sail for the siege and conquest of the city of Ceuta in 1415. This was the first step in opening the Muslim world to medieval Europe, which in fact led to the Age of Discovery with Portuguese explorers sailing across the whole world. By the 15th century, Lagos became the centre of Portuguese maritime exploration, with ships ordered south to trace the shoreline of Africa in order to find routes to India. Infante Henry the Navigator, third son of King John, lived most of the time in Lagos. From here he directed expeditions to Morocco and to the western coast of Africa with caravels, lateen-rigged ships with excellent seafaring capabilities. Lagos was also the home port for Gil Eanes who was the first to sail beyond Cape Bojador in 1434, after a failed attempt in 1433 that put him out of favour with the, then considered the end of the world. The act of rounding the Cape, much like the later rounding of the Cape of Good Hope, permitted Eanes (and the navigators that followed) to advance into the African subcontinent. When, by 1443, Lançarote (then fiscal officer of the crown) had sailed as far as Arguim and brought back 275 Africans, the Portuguese had sufficient slaves to relieve the perpetual handicap of agricultural labour.