The decision in the past few weeks of Governor of the Bank of England Mark Carney to revise his 'forward guidance' on interest rates has been portrayed as an embarrassing about-turn by some. Others, including Mr Carney himself, have quite plausibly argued that his approach has managed expectations effectively. Thus far the markets, the media and politicians seem inclined to believe him.
Mark Carney's important speech set out in some detail the logical steps that are required for a currency union such as the sterling zone to work. It works pretty well at the moment because we have a political union and fiscal and monetary policy work in tandem and banking regulation underpins the system. But would such a system work as well if Scotland were to be an independent country?
There is one clear message from today's thoughtful speech by Mark Carney the Governor of the Bank of England - that the failings of the Eurozone show that to have a successful monetary union you require fiscal and political union. This is a detailed speech but make no mistake, the Governor's judgement on currency unions is devastating for Alex Salmond's currency plans.