On the night of 7 March 1623, the Prince of Wales and the Duke of Buckingham knocked on the door of the British embassy in Madrid. Their unsolicited arrival began one of the most bizarre episodes in British history, as the Protestant heir to the Stuart throne struggled to win the Spanish Infanta as his bride. The prince's visit marked the end of a decade of high-level negotiation to secure a marriage between the leading Protestant and Catholic royal families and heal Europe's century-old division into warring Christian camps. The effort was a diplomatic disaster. It split political and religious opinion in Britain, alienated much of Italy and Germany, confused the Spaniards (who thought that the English crown was about to convert), and failed to secure a marriage or to resolve the Thirty Years War. Drawing on archival material from five countries, Glyn Redworth provides the definitive explanation of this pivotal moment and tells a fascinating story of early modern politicking, cultural misunderstanding, and religious confusion. 'The most convincing account we have. It throws floods of light on the internal and international politics of the early 1620s.' John Morrill, University of Cambridge Glyn Redworth teaches history at the University of Manchester and completed this work while at the Centro de Estudios Historicos, Madrid.