Volatility is back with a vengeance. Having surged almost 45 per cent between mid-March and the end of August, the MSCI All Country World Index, a gauge of global stocks, has since lost 1.5 per cent, and was down by as much as 7.5 per cent in the first three weeks of September.Mounting strains – a resurgence in Covid-19 cases, a sell-off in technology shares, the failure of the US Congress to approve additional stimulus measures and the US’ turbulent presidential election – have put equity…