The Union of 1800-1801 created a single United Kingdom of Great Britain and Ireland. It lasted until the Treaty of 1922 gave birth to what is now the Republic of Ireland; it continues to obtain in Northern Ireland. Patrick Geoghegan's survey examines the passing of the Act of Union in greater detail than ever before, drawing on newly discovered Secret Service papers in the Public Record Office in London. He also connects the passing of the Act of Union to the collapse of William Pitt's ministry in 1801. This is a connection never made before: it gives a depth and context to Geoghegan's survey which makes it stand apart.