Melvyn Bragg and his guests discuss the Siege of Tenochtitlan. In 1521 the Spanish conquistador Hernan Cortes led an army of Spanish and native forces against Tenochtitlan, the spectacular island capital of the Aztec civilisation. After a prolonged siege and fierce battle, the city finally fell. This major confrontation between Old and New Worlds precipitated the downfall of the Aztec Empire and marked a new phase in European colonisation of the Americas. Melvyn Bragg is joined by Alan Knight of the University of Oxford, Elizabeth Graham of University College London and Caroline Dodds Pennock of the University of Sheffield.