Six months ago this week, the world realised the credit party was over. Ever since, the spotlight has been shining on the very core of central banks’ operations – the process of setting interest rates in markets and their skill in easing the first generalised transatlantic liquidity shortage for decades.

None of the institutions at the heart of the crisis – the Federal Reserve, the European Central Bank and the Bank of England – has found the past half year comfortable. The period has been the equivalent of a test-tube experiment in modern central banking, and policymakers now resemble a distinctly uneasy group of scientists: they know what policies they have put into the pot in recent months, but are far from clear why the markets have reacted in certain ways – and even less sure that they have devised the perfect cocktail to stop markets erupting again.