Boris Johnson's reference to the "hair shirt, Stafford Cripps agenda" raises more mischief than perhaps he realises.

This is because Cripps' austerity - even more than the 1980s tightening is an example of expansionary fiscal contraction.

Cripps' fiscal policy was certainly tight. His 1948 Budget, for example, called for "an exceptionally large Budget surplus*." The primary budget balance - which was in deficit of 12.4% of GDP in 1945 - was in a surplus of 3.9% in 1947 when he became Chancellor, and he increased this to over 9% of GDP by 1950.This is a bigger tightening than Osborne is planning; the OBR envisages the primary deficit falling from 5% of GDP in 2011-12 to 1.8% in 2015-16.

However, this tightening - which was achieved mostly by a rise in the share of taxes in GDP - was accompanied by an economic boom. Between 1947 and 1951, GDP grew by 3.5% a year, investment by 5.6%, exports by 11.1% and industrial production by 5.8% a year, whilst the unemployment rate stayed below 1.5%.

Such growth was, of course, facilitated by the massive backlog of investment opportunities which was opened up by the war - including the need to rebuild houses.

And herein lies Johnson's mischief-making. This episode draws our attention to two points.

First, the failure of Osborne's fiscal policy shows not merely that he is a lousy economist, but a poor historian too. A good historian would have asked: under what conditions has fiscal austerity been accompanied by good economic growth in the past? Whether he looked at the early 80s or the post-war period, he would have seen the same thing - that the circumstances in which austerity works are very different from those that exist now.

Secondly, strong growth during the post-war reconstruction period has caused commentators for years to exaggerate the "natural" vigour of capitalism. Between 1948 and 1973, real GDP per head grew by 2.5% a year. But this was exceptional. Since then, it has grown just 1.8% a year, and in the 118 years before 1948 it grew just 1% a year.

In this sense, those who talk about modest growth being the "new normal" are lacking historical perspective. A sluggish economy is in fact the old normal.