“An extraordinary, almost unimaginable sequence of events.” That is how Mervyn King, Governor of the Bank of England, described the circumstances that plunged the world banking system into crisis following the collapse of Lehman Brothers on September 15, 2008. “It is difficult to exaggerate the severity and importance of those events,” he added. “Not since the beginning of the First World War has our banking system been so close to collapse.”

What King was describing is known as a “black swan”, a term made famous by Nassim Nicholas Taleb in his book, The Black Swan: The Impact of the Highly . . .