For a start, the price of credit default swaps, a form of insurance against companies defaulting on debt, went through the roof as investors took cover. AIG, the insurance giant, was carrying a large short position in CDS and faced imminent default. By the next day Hank Paulson, then US Treasury secretary, had to reverse himself and come to the rescue of AIG.

But worse was to come. Lehman was one of the main market-makers in commercial paper and a large issuer of these short-term obligations to boot. Reserve Primary, an independent money market fund, held Lehman paper and, since it had no deep pocket to turn to, it had to “break the buck” – stop redeeming its shares at par. That caused panic among depositors: by Thursday a run on money market funds was in full swing.

The panic then spread to the stock market. The financial system suffered cardiac arrest and had to be put on artificial life support.