How does he get away with it? How does Boris Johnson, a man who demonstrably, shamelessly, obviously cannot be trusted, not simply survive but thrive in politics? A clue could be found in Tuesday’s debate on cutting aid spending.

For months, Conservative MPs have told us how much they hate the cuts, how furious they are that the prime minister is breaking a manifesto promise, how angry they are that they’re not getting a vote. Finally, given a vote, they backed the cuts.

And not just for one year. They have voted for a new “double lock” on aid spending which is likely to keep the cuts until the next election, and beyond. Not that you would have known it to listen to them, of course.

Johnson came to speak at the start of the debate himself. Charity is an issue close to the prime minister’s heart. He has, after all, spent much of the last year trying to set one up to pay for his wallpaper.

“We believe in the power of aid to transform millions of lives,” he began. Indeed, he said, any MP who wanted to make the case for aid to the government was “preaching to the converted.” Good preachers, of course, are aware that unless the converted are addressed regularly, they are in danger of backsliding.

Sir Bob Neill, one of the Tories who has been wringing his hands about the aid cut, rose to intervene. Could the prime minister assure him, he asked, that the double lock was “not a fiscal trap” but instead “a genuine and full-hearted attempt” to get aid spending back to target soon?

“I can indeed give him that confirmation,” Johnson replied.

And who would doubt it? Well, anyone who had heard literally any other promise Johnson has ever made. The former Development Secretary, Andrew Mitchell, for instance, received a series of promises during the 2019 leadership election. It may have been these that he wanted to raise with Johnson when he tried, several times, to ask a question, but the prime minister explained that he couldn’t take any more interventions because he wanted to make more time for MPs to speak.

His entire speech had that topsy-turvy quality. He’d abolished the Department for International Development, he explained, because he wanted more people in government thinking about aid. He didn’t want it confined to one department. “My objective was to ensure that every diplomat in our service was actuated by the mission and vision of our finest development officials,” he explained.

Perhaps the Ministry of Defence will get the same treatment, subsumed into the Department for Transport, so that every bus driver is also a member of the SAS.

Was he against aid? Far from it! He was cutting aid because he believed in it so much. We must all pray that we are never the targets of Boris Johnson’s belief.

It was a nonsense speech. As Keir Starmer observed in reply, the prime minister’s unwillingness to take questions even from Conservative MPs may have reflected his own awareness that he was talking gibberish.

Charity is an issue close to the prime minister’s heart. He has, after all, spent much of the last year trying to set one up to pay for his wallpaper

In the hours that followed, Johnson came under plenty of fire, much of it from his own side: Theresa May said the government was breaking a promise “to the poorest people in the world”. Chris Law for the SNP pointed out that despite the shortage of cash, the government was able to find hundreds of millions to pay for a Royal Yacht that the Royal Family is refusing to go near.

David Davis said he considered himself a Thatcherite, but “when I come to choose between money and lives, I always choose lives”. Tom Tugendhat said the prime minister was copying St Augustine: “Lord, make me chaste, but not just yet.” People have accused Johnson of a lot of things over the years, but this must be the first time anyone has suggested he might one day hope to achieve sexual continence.

But the fix was in, and we had known it from the moment Sir Bob Neill spoke. The rebellion had been largely won over by a series of conversations with Rishi Sunak, who as prime minister-in waiting isn’t someone to be crossed lightly.

Bim Afolami was typical, saying how important he thought aid was, how difficult the decision had been , but how admirable it was that the chancellor had come up with clear criteria for when spending would return to target levels, even if, as Afolami acknowledged, those criteria had only been met three times in the last 20 years.

Michael Howard – the eminent military historian, not the former Conservative leader – once observed that “deception can never be effective either in love or war unless there is a certain willingness to be deceived.” The Tory party is, it turns out, desperate to be deceived.

Sunak spoke to wrap up the debate, making about as much sense as Johnson. Aid, he explained, was vitally important, and it must be cut. He said he knew that for many, aid was a matter of conscience, and that he felt that too.

Not many people would have the confidence to quote Scripture to explain why they were going to stop giving food to starving people, but Sunak does. He cited Paul’s letter to the Corinthians — “Charity is patient, is kind” – and said that explained his position. Sadly he didn’t expand on this. Perhaps he is under the impression that the apostle was describing the Red Cross, and saying they wouldn’t mind waiting a few years for cash.

Earlier, Mitchell had warned his colleagues of the reputational dangers of breaking such a clear promise on such an important issue. “There is an unpleasant odour wafting out from under my party’s front door,” he said. “This is not who we are.”

Unfortunately, as it says elsewhere in the Bible: “by their fruit you will recognise them”.