Dr. Sam Willis concludes his history of the weapons that have shaped Britain by looking at the drive to develop ever more precise weapons on the battlefield, from artillery shells to rifles to the Maxim machine gun. He test fires a 'Brown Bess' musket, the infantry weapon of choice at Waterloo in 1815; he tells the story of Spencer Percival, the only British prime minister ever to be assassinated, shot at point blank range in the lobby of the House of Commons in 1812; and he finds out whether a bulletproof vest made of silk might have stopped a bullet fired at Archduke Franz Ferdinand, which led to the outbreak of World War I.