Anyhow, the four years since Osborne's adoption of fiscal austerity have seen rising demand and output in Britain, and remarkably high growth of employment. As after the 1981 Budget and the USA's early 2013 fiscal cliff, reductions in the budget deficit have been consistent with the net creation of new jobs. (A drop in public employment has been exceeded by increases in private employment.) If the Keynesians want to regard Osborne's fiscal policy as another laboratory experiment, fine, and let them again eat their words. They were vocal, even outspoken, in condemning a nation that wanted to have stronger public finances, and once more their forecasts have proved invalid.

To give the IMF its due, it has acknowledged openly that it was wrong. This year British economy is expected to enjoy the fastest rate of growth among the advanced nations, with an almost 3 per cent output gain. At a press conference in Osborne's presence in June, Christine Lagarde, the IMF's managing director, conceded that "we clearly underestimated the growth of the UK economy". She even granted that "the planned fiscal adjustment this year is appropriate". But Lagarde is a talented politician-cum-international-bureaucrat, not a professional economist, and — like most movers and shakers of her kind — she blows with the wind. Can any of the economists — Summers, Krugman, Wolf and so on — accept that they have been in error?

Martin Wolf has had the opportunity to review his contributions to the debates in a recently-published book, The Shifts and the Shocks: What we've learned — and have still to learn — from the financial crisis (Allen Lane, £25). The title implies a certain modesty, suggesting that Wolf still has not reached equilibrium in his views on these difficult questions of public policy. But, as regards fiscal policy and Osborne's "huge gamble", Wolf has learned nothing. George Osborne himself is not mentioned. There are snide remarks about "expansionary fiscal contraction" in chapter seven, plus the implausible claim that fiscal retrenchment in 2010 was "premature and unwise". But there is no hint of apology or rethinking.

The truth is that Wolf's April 2011 article was not about fiscal policy in the one year of 2010, but about Osborne's five-year strategy which stretched out to 2015/16. The phrase "huge gamble" referred to the planned multi-year programme of fiscal restraint. In the event the fiscal consolidation has not been as substantial as originally envisaged and a large deficit remains. In 2009/10, the final year of New Labour, public sector net borrowing was just over £150 billion. This had come down to £98 billion in 2013/14, but the latest numbers suggest that the 2014/15 outturn will still be above £100 billion. Nevertheless, the IMF calculates that the budget position (cyclically-adjusted) has been "tightened", in Keynesian language, by almost 5 per cent of GDP since 2009. The Osborne "fiscal tightening" has indeed been of much the same size, relative to GDP, as that in the five years to 1986, which led to the protests from the 364 30 years ago. Like them, Wolf has been wrong in expecting deficit reduction to result in persistent recession.

How should Osborne or his successor handle the public finances after the next general election? Will the Autumn Statement on December 3 put down some markers? A clear message comes from the 1981 Budget, the 2013 fiscal cliff and the Osborne reversal of Brown's so-called "fiscal expansion", three episodes which come as close to laboratory experiments as is possible in the human sciences. The next Chancellor must not be dissuaded from action to lower the deficit by Keynesian bluster that such action will inevitably weaken demand and destroy jobs. He or she must pledge a return to a balanced budget, even if contrary advice is given by the Financial Times. The Financial Times remains a massively influential newspaper with much interesting writing, but its chief economics commentator has become too fond of wearing his Keynesian heart on his left-leaning sleeve.