I t is part of the modern Budget ritual to have the Institute for Fiscal Studies , the respected and impartial think tank, pour cold water on the fireworks let off the day before. The IFS did its duty today, pointing out that, behind the facade of a cautious, small-measures Budget , John Healey took more risks with the future than were immediately evident.

Helen Miller, the director of the IFS, was particularly stern about the chancellor’s decision to dip into the reserves to pay for the Defence Investment Plan – the first instalment of his welcome pledge to raise defence spending to 3 per cent of national income by 2030.

“This is categorically not what the reserves are for,” Ms Miller said. The reserves are for unforeseen contingencies that departments cannot absorb, she said, not for choosing to spend on new commitments.…