This is the first comprehensive study of British policy towards Ireland in the twenty years after the Anglo-Irish Treaty of 1921. The Irish question did not, as some have supposed, vanish with the signing of the Treaty; this study reveals its continued importance in British politics after the Treaty, albeit under the surface. Drawing on recently released official documents, private papers, interviews, and newspaper reports, the author has provided a uniquely detailed picture of opinion which determined British policy in the inter-war years.