ConservativeHome is a pro-aid site.  It shares that view with our members’ panel, at least when we last probed its take in detail.

Like Party members, if the survey was representative of their views, we stand solidly behind the core functions of aid: emergency relief, water provision, sanitation, immunisation.  Like them again, we are dubious about the returns gained from using aid as an instrument for economic reform or better governance.

This is why we opposed the abolition of DfID, believing that it made no sense to scrap a department geared to helping some of the poorest people in the world.

But this site has never been able to see why it makes sense to spend a particular percentage of GNI on overseas aid.  If a government does so, it follows that it may sometimes spend money on aid projects simply to hit the target, rather than because it has schemes to hand which it believes will work.

Our guess is that this position is broadly that of many Conservative MPs.  Nonetheless, we are not sure that the Government will be able to abandon the 0.7 per cent, even temporarily, if it tries, for two main reasons.

First, the Conservative Manifesto declared that “we will proudly [our italics] maintain our commitment to spend 0.7 per cent of GNI on development”.  It is sometimes necessary to break manifesto pledges, but there should be a strong presumption against it.

And there is also a great deal more at stake here than the aid budget alone.  For example, consider the topical subject of  today’s Spending Review.  There is talk of tax rises from the Institute of Fiscal Studies, and many others.

“We will not raise the rate of income tax, VAT or National Insurance,” the manifesto also said.  But those three taxes between them account for almost two-thirds of the tax take.  Capital, property and corporation taxes raise about a quarter.

So if the Chancellor judges large-scale tax rises necessary at some point, why should he stick to the former rather than raid the latter, too – using exactly the same arguments about necessity as would be deployed in relation to aid?

Indeed, these could be applied to all other manifeso commitments: tax is merely a timely example.  So some Tory MPs unsupportive of the 0.7 per cent target will view any move to water it down with suspicion.

Next, it may be that a Bill will be required to implement any change.  Why?  Because MPs from all parties took the virtue-signalling option of putting the target into law.  There is wiggle room in the legislation for governments missing the target, but none that we know of for one declaring that it intends to miss it.

So any attempt to drop the target will immediately be taken to the courts.  Do we really need to say again that putting targets into law is a thoroughly bad idea?  (See here and here.)

If there is to be a target, MPs ought to have maxiumum flexibility in debating and changing it.  They lack this room for manoeuvre over the 2050 zero emissions target, too.  Some future government may find itself striving to unscramble that target in the same way that this one is doing over the 0.7 per cent.

We will find out today whether Rishi Sunak intends to proceed with a reduction.  If he does, he and Boris Johnson will have a fight on his hands.

For the row over the 0.7 per cent is becoming a proxy for a struggle between resurrected Cameroons, risen from their unquiet graves, with their more consensual conservatism of which the target was an integral part…and a Conservative leadership that swept through the Red Wall last year as the Party of Brexit.

David Cameron has caused less trouble for Boris Johnson, since last December, than the former leader who came between them – Theresa May.  Indeed, he has been a loyal trouper, pretty much.

Watch how carefully he sought to tread a middle way between criticising the Government and supporting it during the row about the proposed potential breaking of international law in the event of a No Deal Brexit.  But the 0.7 per cent is a founding article of Cameroon faith, and he isn’t holding back in speaking out.

So are Jeremy Hunt, Ruth Davidson, Andrew Mitchell and Damian Green, who chairs the One Nation Group of Conservative MPs.

We wouldn’t be at all surprised if the Chancellor hedges the issue this afternoon, especially if there are few retrenchments elswhere.  A majority of 80 is one of near-landslide proportions – but Covid-19, Brexit trade, all those Research Groups, all that Whatsapping and long-term changes in Parliamentary culture mean that it isn’t what it was.

If Johnson and Sunak decide to press ahead, the 0.7, like the Government’s housing plans, may become a test of whether it can get significant change through this Commons at all.