Can chancellor survive NI U-turn?

This has been a mega shambles Budget - worse than Osborne's notorious omni-shambles.

Because the judgement at the centre of it, that a manifesto-breaching rise in National Insurance would fund £2.4bn of emergency support for social care for the elderly, has imploded.

The fall out has been briefing and counter-briefing by the Treasury and Number 10 - about who was to blame. It's messy and unpleasant.

And although the prime minister is damaged by the charge that she should have seen that her MPs would not wear the tax rise, under the British system budgets belong to chancellors.

At the nub of the issue is why Philip Hammond and the Treasury under-estimated the gravity of breaking such an unambiguous election promise.

What is striking is that one of the most influential figures in the party praised the PM for acting decisively to lance the boil.

And it speaks volumes that neither he nor any other Tory MP to whom I've spoken has tried to defend Hammond.

As for the prime minister's official spokesman, his statement that she has "full confidence in the chancellor" is a formula often taken as a nod to the inhabitant of Number 11 that his tenancy is almost up.

Trust has seriously broken down between the two centres of authority in the government.

Hammond is seriously weakened, perhaps fatally so.

Senior Tories, including ministers, are openly talking about who could and should replace him - and not just because of the Budget debacle but because they also see him and Treasury officials as obstacles to the kind of so-called clean Brexit they want.

So as I said on ITV's Evening News, I would not wager vast sums on Hammond remaining as chancellor beyond the summer.