Chancellor George Osborne presented another hyperactive Budget combining apparent fiscal rectitude with a range of popular measures. The reality is that his forecast numbers rely on accounting tricks, unspecified future spending reductions and more stealth taxes, and would be blown out of the water by another recession or a rebound in borrowing costs.

As expected, the Office for Budget Responsibility revised up its baseline borrowing numbers significantly, despite another cut in forecast debt interest payments, reflecting greater pessimism about trend productivity growth. How, then, did Mr Osborne manage to claim that he remains on track to achieve a fiscal surplus of more than £10 billion in 2019-20 and 2020-21?

There were two main tricks. First, he shifted a significant chunk of revenue from 2017-18 and 2018-19 into the two later years by delaying a previously-announced acceleration of corporation tax payments. That is, he will borrow more in 2017-18 and 2018-19 to “fund” his surpluses in the later years.

Secondly, he pencilled in large but unspecified cuts in current spending in 2019-20 and 2020-21. He disguised part of this reduction as an increase in pension contributions by public sector employers – these higher contributions will be met from existing budgets, implying that savings must be found elsewhere.

The remainder of the Budget consisted of more tax system meddling to conjure up revenue to fund his populist announcements. A problem here is that the additional yield from the revenue-raising measures is more uncertain than the cost of the giveaways.

As usual, the Chancellor expects a further attack on “avoidance and evasion” to do the heavy lifting, with a list of 14 measures forecast to raise more than £3 billion in 2019-20. This essentially pays for the announced increases in the personal allowance and higher rate thresholds, generous changes to the ISA regime and another fuel duty freeze.

The business tax changes are similarly self-financing, with cuts in a range of exemptions benefiting large corporations and higher stamp duty on commercial property transactions used to fund a big rise in rate relief for small businesses and a reduction in the main corporation tax rate to 17%.

Contrary to the Chancellor’s claims, there is still a gaping hole in the UK’s fiscal roof. Lowered spending targets will be tough to achieve and the OBR’s forecasts also rely on doubly-favourable assumptions of sustained economic growth and little rise in interest rates. For all his bravado, Mr Osborne may be hoping for a move out of no. 11 before the economic weather changes.