This was a huge, change-making budget.

Don’t let anyone tell you there isn’t much difference between the main parties at Westminster.

This was a Budget with Labour’s instincts and worldview stamped throughout it.

There are the tax rises visible from near-earth orbit, the self imposed borrowing rules shredded and re-written – to allow more borrowing – and big wads of spending for the NHS, just for starters.

I lost track during the election campaign of how often Labour folk insisted they had “no plans” to put up taxes beyond a relatively narrow band of those they said would rise.

Looked at now you don’t have to be wildly uncharitable to conclude that was comprehensive baloney.

Labour, psychologically scarred by losing far more elections than they win, tend to try to hug the Conservatives close when it comes to tax and spending plans before elections where they think they can beat them, fearing anything else will spook swing voters and cost them the contest.

And, pretty much, that is what Labour did back in the summer.

No such caution now.

The books were worse than we thought is Labour’s mitigating plea, garnished with a we-won’t-do-it-again insistence from the chancellor in my interview with her.

“This is not the sort of Budget we would want to repeat,” Rachel Reeves told me.

For the chancellor, we now enter the valley of maximum scrutiny and jeopardy for her prospectus.

Journalists, policy experts, industry, trade unions, you as readers have a chance to properly squirrel away at the detail and ask awkward questions.

You will see the chancellor on BBC television and hear her on the radio.

Senior figures insist they want to embrace this scrutiny.

They point out she didn’t go on TV and radio shows last Sunday, before the Budget, as has become recent infuriating tradition – where journalists ask pertinent questions about the content of the Budget and are repeatedly told to wait until Wednesday.

She will instead be appearing this Sunday, alongside the new Conservative leader elected on Saturday, no doubt.

So where might that scrutiny come? All the big stuff, for sure – the tax rises, the borrowing, the spending.

But I always like to keep an eye on the rows that may appear smaller but have the potential to blow up in a government’s face.

There is already real anger among many farmers about changes to inheritance tax which they fear will mean lots of farming families will no longer be able to pass on their life’s work and business to the next generation.

And a couple of big picture, longer-term thoughts to ponder.

This is a government with a central mission of helping to drive up economic growth.

And yet the projections for growth appear stubbornly anaemic, as our economics editor, Faisal Islam, writes.

And there is a similar observation from the Institute for Fiscal Studies, who have crunched the numbers on the forecasts for the money we are each likely to have in our pockets in the coming years, once bills are sorted – per capita disposable income, to use the language of economists.

They conclude its rate of growth, while up a smidgen on where it’s been in recent years, is still pretty piffling.

The government will hope the forecasts are wrong – and they can be.

But, as I have written before, what seems to be a huge contributor to the anti-politics mood as well as wild political volatility is that unshiftable financial reality for many: the brutal truth that things haven’t got much better, if at all better, for ages and ages and ages.

And, in the end, the persistence of that trend, or its marked end, will matter more to millions of people and the likely eventual fate of this government than plenty of the other Budget numbers being picked over right now.

At the Budget, Chancellor Rachel Reeves once again blamed the Conservatives for leaving a “£22bn black hole” in the public finances.

A report from the Office for Budget Responsibility (OBR), which makes forecasts for the government, found there had been information it should have been given by the Treasury, but only listed a £9.5bn shortfall from February.

Nonetheless, it said forecasts in March would have been “materially different” if it had known about all the previous government’s spending plans.

Conservative leader Rishi Sunak said the OBR had declined to support Reeves’s claims of a £22bn black hole, saying: “It actually appears nowhere in their report.”

Reeves said the £22bn came from the £9.5bn of spending plans reported by the OBR from February, another £7bn before the March Budget, and a further £5.6bn between March and the end of July, including public sector pay awards made by Labour.

Government ministers have repeatedly used the figure to justify the decision to cut the winter fuel payment and raise taxes.

Accompanying a Budget that increased spending by £70bn a year, the OBR published a report on 30 October looking at whether there had been information about pressures on spending that it should have known about in February when it was working on its forecasts to go with the March Budget.

It asked the Treasury for an estimate of these pressures and was given a figure of £9.5bn, which is considerably below the £22bn in the July report.

“Had we known that information we would have had a materially different view about the level of public spending this year,” OBR head Richard Hughes told BBC News.

“We can’t say how different that would have been because we would have had to have had a different conversation with the Treasury in the light of that information.”

Reeves told BBC News that the rest of the £22bn was overspent between the Budget and the 4 July election.

Paul Johnson, director of the Institute for Fiscal Studies think tank said Reeves “may be overegging the £22bn black hole”.

The government published a breakdown of how it had got from the Treasury’s £9.5bn shortfall in February to the £22bn “black hole”.

It said that there was another £7bn between February and the actual Budget in March, as departments found out about new spending pressures and the government spent more on the NHS and the Household Support Fund

There was a final £5.6bn between then and late July, which includes almost a month when Labour was in power.

That was largely caused by increases in public sector pay.

It was the Labour government that accepted the recommendations of the Pay Review Bodies (PRBs), but they said that the previous government should have budgeted for more than a 2% increase in public sector pay.

Prof Stephen Millard from the National Institute of Economic and Social Research think tank told BBC Verify: “The ‘political’ question is whether you would count this as part of the fiscal black hole or not. If you do, then you get to the £22bn figure; if not, then you’re left with around £12.5bn to £13.5bn.”

To put those figure into context, in the Spring Budget it was expected that total public spending this year would be £1,226bn. Either £9.5bn or £22bn would be a small proportion of that.

But by the standards of government overspends, either would be unusually large.

Spending was much higher than expected due to Covid in 2020 and 2021 and also almost £10bn higher than expected in 2023 because of inflation caused by Russia’s invasion of Ukraine.

Outside those years there have not been overspends close to £9.5bn.

This piece was originally published on 3 September 2024 and has been updated following the OBR report that accompanied the 30 October Budget