In 1816, the net public debt of the UK reached 240 per cent of gross domestic product. This was the fiscal legacy of 125 years of war against France. What economic disaster followed this crushing burden of debt? The industrial revolution.

Yet Carmen Reinhart and Kenneth Rogoff of Harvard university argued, in a famous paper, that growth slows sharply when the ratio of public debt to GDP exceeds 90 per cent. The UK’s experience in the 19th century is such a powerful exception, because it marked the beginning of the consistent rises in living standards that characterises the world we live in. The growth of that era is the parent of subsequent sustained growth everywhere.

As Mark Blyth of Brown University notes in a splendid new book, great economists of the 18th century, such as David Hume and Adam Smith warned against excessive public debt. Embroiled in frequent wars, the British state ignored them. Yet the warnings must have appeared all too credible. Between 1815 and 1855, for example, debt interest accounted for close to half of all UK public spending.