Melvyn Bragg and guests discuss the debate in Valladolid, Spain in 1550, over Spanish rights to enslave the native peoples in the newly conquered lands. Bartolomé de Las Casas (pictured above), the Bishop of Chiapas, Mexico, was trying to end the encomienda system in which those who now owned the land could also take the people in forced labour. Juan Gines Sepulveda, a philosopher, argued for the colonists' property rights over people, asserting that some native Americans were 'natural slaves' as defined by Aristotle. Valladolid became seen as the first open attempt by European colonists to discuss the ethics of slavery, and Las Casas became known as 'Saviour of the Indians' and an advocate for human rights, although for some time he argued that African slaves be imported to do the work in place of the native people, before repenting. With Caroline Dodds Pennock Senior Lecturer in International History at the University of Sheffield John Edwards Faculty Fellow in Spanish at the University of Oxford And Julia McClure Lecturer in Late Medieval and Early Modern Global History at the University of Glasgow Producer: Simon Tillotson