The Bank for International Settlements’ annual report in 2009 surveyed a financial system that was “critically damaged”. Before the crisis there had been danger signs and some parties issued warnings – “most were in vain”. The report traces the roots of the crisis to a mixture of human behaviour and policy mistakes, and notes it is easy to see why warnings fell on deaf ears. Understanding the nature of such events is difficult when they are so infrequent, and making “what would have been