On 23 February 1820 a group of radicals were arrested in Cato Street off the Edgware Road in London. They were within sixty minutes of setting out to assassinate the British cabinet. Five of the conspirators were subsequently executed and another five were transported for life to Australia. The plotters were a mixture of English, Scots and Irish tradesmen, and one was a black Jamaican. They were motivated by a desire to avenge the ‘Peterloo’ massacre and intended to declare a republic, which they believed would encourage popular risings in London and across Britain. This volume of essays uses contemporary reports by Home Office spies and informers to assess the seriousness of the conspiracy. It traces the practical and intellectual origins of the plotters’ willingness to use violence; describes the links between Irish and British radicals who were willing to take up arms; makes a contribution to early black history in Britain; examines the European context to events, and follows the lives and careers of those plotters exiled to Australia. A significant contribution to our understanding of a particularly turbulent period of British history, these well-written essays will find an appreciative audience among undergraduates, graduate students and scholars of British and Irish history and literature, black history, and the related fields of intelligence history and Strategic Studies.