For a start, it has never actually come about, because it has always been a forecast for future years (from the Office for Budget Responsibility), rather than fact, and it seems contrary to attribute decades of low growth to something that was only a prediction. Taxation over the past quarter of a century, under prime ministers Blair, Brown, Cameron, May and Johnson, has averaged 32.8% as a proportion of economic output, or GDP. Under Mrs Thatcher’s 11 years that number was 32.4% of GDP.