It was all going so well. Comedy Philip Hammond stepped up to the despatch box to deliver his first Spring Budget as chancellor via the medium of a stand-up routine. Joke after joke was fired across the House of Commons at the Labour benches.

But now the joke's on him. And one of Hammond's Budget jokes in particular appears a touch hubristic.

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Hammond is scrapping the Spring Budget and moving it to Autumn, where it will replace the Autumn Statement, meaning there's only one of these events a year instead of two.

"Twenty-four years ago Norman Lamont also presented what was billed then as 'the last Spring Budget'," Hammond said. "He reported on an economy that was growing faster than any other in the G7, and he committed to continued restraint in public spending.

"The then prime minister described it as the 'right budget, at the right time, from the right chancellor'. What they failed to remind me was... 10 weeks later, he was sacked! So wish me luck today."

How amusing. How self-deprecating. How... prophetic? Of course, it couldn't happen to Spreadsheet Phil. He's a safe pair of hands. He doesn't care about things like popularity. He carries out his Treasury duties with the reliable competence of a robot technocrat.

Turns out he's not as reliable as people thought. Hammond's Budget plan to hike National Insurance Contributions for the self-employed has caused an almighty backlash in the media, from business groups, and among his own party colleagues, not to mention the opposition parties.

There are nearly 5 million people in self-employment in Britain, many of who would have faced a significant cut to their incomes. Jacking up National Insurance was always going to be a big political ask, even if it's sound policy to bring them closer into line with what employers and employees have to pay.

And what made it even worse is that it breaches a commitment in the 2015 Conservative party manifesto – on which the party won a majority – not to raise National Insurance.

A war erupted between the Treasury, Downing Street, and the rest of the Cabinet. Treasury officials said they were being asked to balance more spending for "just about managing" families against the need to close the budget deficit, which cannot be done unless taxes rise.

But the Cabinet and Downing Street suggested they were not properly briefed about the hike to National Insurance Contributions, in particular that it would break a manifesto commitment.

As the negative headlines gathered and anger built among Tories, Prime Minister Theresa May told Hammond enough is enough. An unnamed Conservative source told The Telegraph that May said to Hammond: "We are reversing this – I don't care how bad it is for you."

And that was that. The decision was made. Hammond sent a letter making the U-turn, even though some Tory MPs had stuck their necks out by publicly defending the policy. He wrote that he would drop the changes "in light of what has emerged as a clear view among colleagues and a significant section of the public".

"It is very important both to me and to the prime minister that we are compliant not just with the letter, but also the spirit, of the commitments that were made," Hammond wrote.

Hammond's authority has been seriously undermined by the humiliating episode. Other than May, he's also the only senior pro-Remain minister left in the Cabinet. He's surrounded by vehement Brexiteers who would love to have someone from their camp take over the Treasury. They may well smell blood.

Can Hammond survive this? Should he survive? Or will he become the first minister sacked by May since she became prime minister?

Philip Hammond Theresa May