On 16 August 1819, a strong force of yeomanry and regular cavalry charged into a crowd of more than 100,000 workers who had gathered on St Peter’s Field in Manchester for a meeting about Parliamentary reform. Many were killed. This violent, startling event became known as Peterloo, one of the darkest days in Britain’s social history. ‘The Peterloo Massacre’ provides a revealing narrative account of the events leading up to Peterloo, starkly describes the actions of that fateful day, and examines its aftermath. It offers a new perspective on the political and military activities of the time, and shows how the very nature of society was powerfully influenced by irreversible technological change: a pattern that, two-hundred years later, still has relevance in understanding the forces shaping our world today.