“The champions of 0.7 per cent will win either way – if not in the Commons, then in court,” we wrote recently, after a vote to end the reduction from that percentage almost happened.

It didn’t take place because the vehicle for a decision, an amendment to the Advanced Reseach and Invention Agency Bill, was ruled out of order by Lindsay Hoyle.

The Speaker acted correctly.  He was then lambasted on social media for not “being a Bercow” – in other words, acting incorrectly.  That will not in itself have ruffled his feathers.

However, he believes that the Government has been flouting its obligation to make important announcements to the Commons before doing so elsewhere – in particular, those about Covid-19.

That proper resentment will have informed his decision, made public in the wake of the cancelled vote, to ensure that a vote on the 0.7 per cent cut was held in the Commons in due course.

Which brings us to Rishi Sunak, the author of the reduction.  He was staring down the barrel of a Parliamentary defeat – and yesterday evening’s news saw him jerk his head away before the trigger is pulled.

His gambit comes in the form of a “double lock”.  The cut from 0.7 per cent to 0.5 per cent stands.  It will end when aid spending will the Government is no longer borrowing to fund day-to-day spending, and public sector net debt is falling as a percentage of GBP.

Furthermore, the decision about if and when those criteria have been met will be made not by the Chancellor himself, but by the Office of Budget Responsibility.

The Government is gambling on rushing a vote on the proposal through the Commons today, having tried to minimise its retreat by announcing its plan under the cover of yesterday evening’s Covid press conference.

The new policy hasn’t satisfied Andrew Mitchell, the author of the ARIA amendment, but Ministers aren’t straining to appease the former International Development Secretary, whose opposition to the cut is implacable.

Rather, their aim is to peel off enough backbench dissenters to get the policy through.  Much may turn on whether they believe that any reversion to 0.7 per cent will come fast enough: it might not happen for five years or so, though post-Covid growth could speed it.

Three main points arise from this new proposal. First, it emphasises how a majority of 80 won’t always be enough – and signals that, faced with enough opposition from its own MPs, the Government will fold, which sends a signal to seasoned critics and rebels.

If Ministers won’t defend a policy popular with most voters, how fast will they collapse when defending unpopular ones?  The second point is about Sunak himself.

His critics will say that he sought to play to the popular gallery without doing his Parliamentary sums.  His friends say that both he and the Foreign Secretary wanted to hold a vote earlier, before opposition to the 0.7 per cent cut gathered backbench pace.

Finally, the Chancellor is sending a signal about future public spending.  He is reminding Tory MPs that the Conservative manifesto didn’t only make big spending commitments, but also contained a framework for restraint.

When they point out that it promised big increases to find more doctors, police and nurses, he can fire back that it also pledged expenditure control.  Watch this space as the spending review looms into view.

A lesson from this tale is that manifesto promises matter.  We have no particular brief for keeping aid spending at 0.7 per cent, let alone putting that target into law – the driver of the Government’s undoing over its plan for a reduction.

But Ministers can’t break their commitments and expect no consequences.  ConHome is thinking of the pensions triple lock as we write.  And of much else.

The Prime Minister may be a “Brexity Hezza” whose instinct is to spend, spend, spend.  But the Chancellor must follow his incontinent horse with a dustpan and brush.  The Treasury never had much room for manoeuvre, and that space it has is vanishing.