First things first: don’t panic.

What you need to know is this. The budget has not gone down well in financial markets. Indeed, it’s gone down about as badly as any budget in recent years, save for Liz Truss’s mini-budget.

The pound is weaker. Government bond yields (essentially, the interest rate the exchequer pays on its debt) have gone up.

That’s precisely the opposite market reaction to the one chancellors like to see after they commend their fiscal statements to the house.

In hindsight, perhaps we shouldn’t be surprised.

After all, the new government just committed itself to considerably more borrowing than its predecessors – about £140bn more borrowing in the coming years. And that money has to be borrowed from someone – namely, financial markets.

But those financial markets are now reassessing how keen they are to lend to the UK.

The upshot is that the pound has fallen quite sharply (the biggest two-day fall in trade-weighted sterling in 18 months) and gilt yields – the interest rate paid by the government – have risen quite sharply.

This was all beginning to crystallise shortly after the budget speech, with yields beginning to rise and the pound beginning to weaken, the moment investors and economists got their hands on the budget documentation.

But the falls in the pound and the rises in the bond yields accelerated today.

This is not, to be absolutely clear, the kind of response any chancellor wants to see after a budget – let alone their first budget in office.

Indeed, I can’t remember another budget which saw as hostile a market response as this one in many years – save for one.

That exception is, of course, the Liz Truss/Kwasi Kwarteng mini-budget of 2022. And here is where you’ll find the silver lining for Keir Starmer and Rachel Reeves.

The rises in gilt yields and falls in sterling in recent hours and days are still far shy of what took place in the run up and aftermath of the mini-budget. This does not yet feel like a crisis moment for UK markets.

But nor is it anything like good news for the government. In fact, it’s pretty awful. Because higher borrowing rates for UK debt mean it (well, us) will end up paying considerably more to service our debt in the coming years.

And that debt is about to balloon dramatically because of the plans laid down by the chancellor this week.

And this is where things get particularly sticky for Ms Reeves.

In that budget documentation, the Office for Budget Responsibility said the chancellor could afford to see those gilt yields rise by about 1.3 percentage points, but then when they exceeded this level, the so-called “headroom” she had against her fiscal rules would evaporate.

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In other words, she’d break those rules – which, recall, are considerably less strict than the ones she inherited from Jeremy Hunt.

Which raises the question: where are those gilt yields right now? How close are they to the danger zone where the chancellor ends up breaking her rules?

Short answer: worryingly close. Because, right now, the yield on five-year government debt (which is the maturity the OBR focuses on most) is more than halfway towards that danger zone – only 56 basis points away from hitting the point where debt interest costs eat up any leeway the chancellor has to avoid breaking her rules.

Now, we are not in crisis territory yet. Nor can every move in currencies and bonds be attributed to this budget.

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Markets are volatile right now. There’s lots going on: a US election next week and a Bank of England decision on interest rates next week.

The chancellor could get lucky. Gilt yields could settle in the coming days. But, right now, the UK, with its high level of public and private debt, with its new government which has just pledged to borrow many billions more in the coming years, is being closely scrutinised by the “bond vigilantes”.

A Halloween nightmare for any chancellor.