From around 1870, when Britain reached the apogee of its industrial predominance, the country has experienced relative decline as the size of its economy in relation to the rest of the world has fallen. This inescapable process has been accompanied by a recurrent politics and history which have interpreted this decline not as the result of the inevitable competitive rough and tumble development of global capitalism, but as evidence of pathological failings in British society, creating a persistent ‘declinist’ underpinning to accounts of modern Britain. These have suggested that British society has had profound failings in almost all areas—economic, technological, political and cultural. The pattern has been for declinist narratives to be initiated in the political arena, then to be taken up by historians, to be followed in turn by historians rebuttals of such arguments. This pattern can be discerned in the history and historiography of the 1870–1914 period, the inter-war years, and for post-1945. However, it has been strongest for the post-war period, and especially for the years since the Thatcher government of the 1980s. This article outlines these developments, and offers a critique of such declinism as a useful way to understand twentieth century Britain. It suggests that historians have too often in the past based their approach on contemporary, highly politicized and polemical discourses, but that in a number of areas work is now being published which allows us to construct more productive narratives for this period.