“We need a new approach for a new era,” Kwasi Kwarteng declared with relish as he set out his mini-budget last month.  

He certainly delivered the first bit. Rishi Sunak’s political antennae generally stopped him from needlessly infuriating the electorate. But not the second.  

The new Chancellor’s U-turn over abolishing the 45p rate of income tax felt very much like continuity Boris Johnson.  

Instead of owning up to an obvious error, Downing Street dug in, ministers were dispatched to defend the indefensible, until, faced with internal revolt and public anger, the offending policy was ditched, leaving all its advocates looking like fools. 

However you cut it, this was a self-inflicted disaster for the Tories.  

It has been all pain, no gain.  

Instead of getting credit for their £150 billion energy bill package, the Government’s intervention was eclipsed by a row over a policy costing a relatively meagre £2bn.  

That and the currency and mortgage chaos unleashed by the rest of the budget, of course. 

And instead of coming over as a fresh start, Liz Truss and Mr Kwarteng reminded voters they are very much part of the same lot who have been withering in office since 2010. It doesn’t feel like a new era, but a descent of the last shambles into something worse.  

A key reason the Bank of England intervened last week with £65bn to buy UK Government debt was fear of contagion. 

City jitters about Mr Kwarteng’s £45bn of unfunded tax cuts and talk of more to come had forced up the cost of Government borrowing and tanked Treasury gilts. 

That created a risk of pension funds collapsing as the value of their gilt holdings slumped, and of instability then rippling out across the economy, triggering shocks not just in the UK but globally.  

The PM and Chancellor are now threatened by political contagion: the risk that the mistakes and climbdown over the mini-budget define and undermine them so much that they cannot make a decent fist of anything else.  

It’s worth remembering that Ms Truss started her premiership without a honeymoon period. There was no bounce in the polls when she took over a month ago. Nor was there party unity. She had been backed by a minority of Tory MPs in the leadership race, and she then entrenched those party divisions by sacking Rishi Sunak’s supporters from her government.  

There are now lots of unhappy, highly articulate critics on her backbenches ready to lash out. 

Michael Gove and Grant Shapps were instrumental in bringing about the U-turn on the 45p income tax rate by labelling it un-Conservative and unsellable given the cost-of -living crisis. 

There were also heavy hints about the measure being voted down in the Commons. 

Less than 24 hours after being “absolutely committed” to the tax cut, Ms Truss and the Chancellor had to bin the wretched thing. It was humiliating, but not as bad as losing a vote in parliament and then being forced to drop it. 

But this is far from the end of the matter. The huge borrowing which spooked the markets is essentially unchanged. More crises loom when the Bank of England ends its gilt-buying spree soon. 

Ms Truss and her Chancellor are diminished, their authority damaged, possibly beyond repair.   

They didn’t have much political capital in the first place, but what little they had has been burnt through at extraordinary speed. 

Tax breaks for the rich and welfare cuts for the struggling was always a disastrous combination, a U-turn waiting to happen.  

Its authors looked heartless doing it, then weak undoing it. 

Now that 10 and 11 Downing Street have blinked once, Tory rebels will be emboldened. And there are many more battles to come, not least on the planning reform Mr Kwarteng promised.  

City traders will also wonder what else the Government plans to ditch – and if they can make a killing by testing ministers’ resolve. 

So the PM faces serial rebellions in the Commons, more turmoil in the markets and opposition parties riding high in the polls, worsening the indiscipline of her MPs .  

“What a day! It has been tough,” Mr Kwarteng told the Tory party conference yesterday.  

He ain’t seen nothing yet.