According to his most eminent recent biographers, there is not a single piece of documented proof that economic sage John Maynard Keynes ever uttered the oft-attributed phrase: ‘When the facts change, I change my mind – what do you do, Sir?'

But barely two months since March's Budget, has the hard evidence-base supporting the Treasury's assumptions really experienced a similarly dramatic shift when faced with reality? Or is it the case that those musty official ideas, long locked in Excel cells for annual appraisal, were kept by previous ministers for the sound reasons that they were politically untenable? Exposure to the disinfectant of sunlight has borne this reasoning out on charities tax relief, church repairs, caravans and those comedy pasties.