“He’s giving up income to do this job.” David Davis was explaining to the BBC why, when you thought about it, we are tremendously lucky to have Rishi Sunak as a prime minister. It’s tempting to think he was being sarcastic, but I fear he was genuinely trying to help.

All Friday, the Conservatives wallowed in their self-inflicted hell

Friday June 7, or, as I now think of it, D Plus One, was proving to be the worst day of the Conservative election campaign. The worst day of the election campaign so far, anyway. I’ll admit to having felt a pang of guilt on Wednesday after suggesting that Sunak was running his campaign with the sort of impressive touch that puts you in mind of a goldfish attempting quantum physics. I stopped feeling bad when we learned that the prime minister had bunked off the D-Day commemorations for a TV interview.

Often at these moments when it looks like someone has made a catastrophic mistake, I’ll find myself explaining that there is actually an obscure logic to their actions. Not this time. Economists talk about “Pareto Improvements”, which make something better in every way. On Friday we saw in the wild an example of a phenomenon whose existence had previously only been theorised: a Sunak Deterioration, an act that simply makes everything worse.

When it first turned out Sunak had left Normandy early, there was a thought at the back of journalists’ minds that there might be a very serious reason for this, some unavoidable briefing about an imminent national threat. In fact, he’d just wanted to go and repeat some things that weren’t true to ITV.

All Friday, the Conservatives wallowed in their self-inflicted hell. And pretty much the first thing that happened on the BBC’s seven-way debate that evening was that the Conservative party’s representative denounced her own leader.

“What happened was completely wrong,” Penny Mordaunt said, looking very much like she meant it. “The prime minister has rightly apologised.” It was, she said again, “very wrong – he was there representing us.” Has there been a moment in British politics like it? Not even an attempt to defend his actions, simply a hope that everyone will forgive and forget.

After that an interesting dynamic emerged. Rayner and Mordaunt, next to each other at one end of the stage, were the main action, accusing each other of every horror under the sun. Rayner was going to put up your taxes and refuse to fire nuclear weapons. Mordaunt was a liar whose party had crashed the economy. Rayner was stiff at first, but warmed up once Mordaunt had begun interrupting her. “My brother served in Iraq,” Rayner told Mordaunt during one discussion about patriotism. “I won’t be lectured!”

Mordaunt meanwhile hammered her own point. “Even Liz Truss on her worst days would still recognise that we need a nuclear deterrent in this country,” she said at one stage, which was perhaps intended as a killer line but was also her second attack on a Tory prime minister in the space of an hour.

The other five were in their own private spaces. Stephen Flynn of the SNP and Rhun ap Iorweth of Plaid Cymru were in their own countries, where good things are down to them and everything else is Westminster’s fault. Asked about broken political promises, Flynn could reply confident that no one was going to contradict him: “In a Scottish context I can offer you a few that are being delivered.” Goodness, Scotland sounds like a terrifically well-run place. It makes you want to jump in a campervan and explore its glories. It’s strange that, given the earthly paradise that the SNP has built there, Flynn is projected to be leading a much smaller team of MPs next month.

He could, after all, be earning much more doing something else

Daisy Cooper was present for the Lib Dems, but I find I wrote down nothing that she said. Carla Denyer of the Greens continued to work at sounding vague-but-nice. Her waffling down of the clock when asked about her party’s defence policy was a masterclass. “But the biggest threat to the world is climate change!” she declared, just as time ran out. There was sadly no time to interrogate her position on NATO.

And then there was Nigel Farage, stage left, panel far-right. All these debates are a tug-of-war between promises of decorum and the producers’ desire for televisual moments of drama. That leaves little incentive to, say, cut someone’s microphone, and ultimately rewards people who ignore the rules. This has always been Farage’s strong suit. He talked over Husain, heckled Denyer, interrupted as he saw fit.

No one, on the other hand, talked over him. Not Mordaunt, whose party has the most to lose from a Reform surge. Flynn briefly tried but gave up. The only person who posed much threat to Farage was Farage, his enthusiasm for replacing the NHS with an insurance-based model being something that is unlikely to go down well with the voters of Clacton, if he mentions it to them.

Back, though, to the unhappy prime minister. Around lunchtime he delivered a weary, snippy clip to Sky News in which he explained repeatedly that he’d “participated in all the British events with all the British veterans” before leaving.

But his claim that his departure had been planned “weeks ago” made things sound worse. It was impossible to escape the thought that, faced with two whole days of world leaders and national anthems and flypasts and veterans, the prime minister had asked how much of it he really had to sit through. And that, having sat through it, he thought we ought to be grateful to him for doing so. He could, after all, be earning much more doing something else.