Numerous books have been published about the First World War but few have focused on the machinations in the British parliament and the role it played in the decision to go to war. Britain, after all, could not have entered the conflict without clear approval from MPs. One hundred years on, Fatal Fortnight reexamines the arguments which Parliament heard against British war entry and reflects on how the world might have been had the decision gone a different way. At the center of the stormy debate was the enigmatic Arthur Ponsonby. Born into the heart of the aristocracy, the son of Queen Victoria’s Private Secretary and pageboy to the Queen, Ponsonby was a champion of social reform and of democratic foreign policy. His grandfather fought at Waterloo and his brother was a Brigadier who served on the Western Front; he himself loathed war and sought alternatives, and as Chairman of the Liberal Foreign Affairs Committee he led the backbench battle to try to keep Britain out of the 1914 war. Alongside the unraveling political drama a human story emerges of how family support for Ponsonby and his allies sustained them as the world closed in.