British historian Dan Snow visits a major Lodon exhibition and many Mexican sites, first to illustrate the grandeur of the Aztec empire at its peek, under emperor Montezuma II (1466-1520), who inherited it from an uncle and installed a reign of utter terror. Then to show its downfall, at the hands of Hernan Cortez's small but militarily superior band of veteran dogs of war, who ironically turned horrified vassals against Montezuma. Dan also discusses precious sources and myths.