Will no one rid me of this turbulent central banker? Gordon Brown, the UK's prime minister, may be asking just that when he learns of yet another critical comment from the governor of the Bank of England. For Henry II, king of England in the 12th century, the troublemaker was Thomas Becket, his own choice as archbishop of Canterbury. For Mr Brown, it is Mervyn King, whom he has reappointed to an equally impregnable position. The parallel is clear: central bankers are cardinals in the cult of monetary stability.

Becket was murdered. Mr King will not suffer that fate. But a later king of England brought the church and his archbishops to heel. Could the Bank suffer a similar fate?

Indeed, one of the results of this crisis is to imperil central bank independence, not just in the UK. This is so for three reasons: at close to zero official interest rates, the boundary between monetary and fiscal policy erodes; governments are running huge fiscal deficits, particularly in the UK and the US, which threaten monetary stability; and, finally, those in charge wish to divert blame for the disaster.