In their patter song in The Pirates of Penzance, Gilbert and Sullivan satirised the notion of an educated “modern major-general”. Today they might satirise academic central bankers, of which Ben Bernanke – soon to be ex-chairman of the Federal Reserve – is the very model. As a distinguished scholar, he brought to the Fed a brilliant and well-informed mind. His knowledge of economic history helped him halt a terrifying panic. But he also made mistakes. History will probably judge him kindly. But there is much to be learnt from his time at the Fed.

Mr Bernanke was hugely influential even before he became chairman, in 2006. As governor from 2002, he made notable contributions, including his 2002 “Making Sure ‘It’ [Japanese-style deflation] Doesn’t Happen Here”, and his 2004 celebration of the “Great Moderation”. Before this, not least in a 1999 paper co-authored with Mark Gertler of New York University, he had argued that “the best policy framework for attaining [price and financial stability] is a regime of flexible inflation targeting”. This is the core dogma of modern central banking.

In a valedictory this month, Mr Bernanke started with “transparency and accountability”, pointing to the fact that, in January 2012, the Federal Open Market Committee “established, for the first time, an explicit longer-run goal for inflation of 2 per cent”. He added that the Fed’s transparency and accountability proved “critical in a quite different sphere – namely, in supporting the institution’s democratic legitimacy”. He was surely right. Central banks wield great power. Transparency and accountability are vital if its exercise is to be both effective and legitimate.