Second-guessing the actions of central bankers has always been a tricky business. The Bank of England governor Mark Carney’s policy of forward guidance was meant to make this job easier, tying monetary policy to the unemployment rate.

However, when unemployment fell faster than expected and the Bank of England judged that the economy wasn’t yet ready for higher interest rates, the goalposts were moved.

The second incarnation of forward guidance saw the Bank targeting the degree of ‘slack’ in the economy. Unfortunately, not even the Bank itself seems clear on how to measure ‘slack’, or even how to define it.

It is this lack of clarity which prompted one Treasury committee member to accuse the Bank of behaving like an unreliable boyfriend.