It is quite a moment when a trusted national statistical agency reveals that it has lost its independence from central government. That happened last week in Britain. As of Thursday,

the Office for National Statistics is no longer producing consistent and reliable estimates of the public finances. Worse, the mistakes it has made would have been easily avoidable if it had learnt a simple lesson from the financial crisis.

In the years before 2007, the leading credit rating agencies traded on their reputations as independent experts. Using intricate risk models, they gave triple A ratings to fiendishly complex derivative securities. When the crisis struck, the detailed modelling was exposed as useless. The agencies had failed to see the wood for the trees. Their reputations dived.