The second quarter may well have marked the bottom. But it could also descend into infamy as the most deceptive three months in economic memory. Certainly all the talk of a second Great Depression has vanished. Equity markets are up by between a 10th and a third and data are better across a range of economic indicators.

Such renewed optimism is uplifting. But this crisis was supposedly caused by decades of malign economic and financial forces. Do things turn round in one quarter? Japan, for example, remains bedridden almost 20 years after its meltdown. For this crisis to be over so soon, investors have to believe that the initial collapse was exaggerated and that the old world was not so sick after all.

Many share that view. The price/earnings ratio of the S&P 500, which jumped from about 10 to 15 times over the quarter – above its long-term average – reflects a return to more normalised earnings. Measures of global shipping rates have surged almost 400 per cent since January 1. Commodities from soyabeans to copper have doubled. Meanwhile, longer-term bonds are drifting back to sensible yields and indicators of volatility are back to pre-Lehman levels.

Yet these moves can also be viewed through a darker lens. Plummeting demand has only moderated due to stimulus policies and zero interest rates. Neither is sustainable. There may be a minibubble in commodities, additionally inflated by Chinese hoarding. All over the world, household, corporate (and now government) balance sheets are overleveraged.

It is not scaremongering to worry that the second quarter was just a blip. Indeed, Tuesday’s worse-than-expected consumer confidence data in the US suggest optimism may now be ebbing away.