On days like these you reckon the prime minister would have more chance of being believed if he had said the dog ate his homework. After all, it’s quite possible that Keir Starmer has not yet realised he doesn’t have a dog. His amnesia and lack of curiosity are a piece of performance art. Almost up there with Boris Johnson. Keir would probably take that as a compliment.

As it is we are left with a dilemma. Occam’s razor. Either No 10 thinks we were born yesterday. Or everyone in No 10 was born yesterday. The excuses factory has been working overtime. But most people have already made up their minds.

No one can possibly have been quite so half-witted as to not take an interest in the security vetting of a man almost everyone knew to be so controversial. Who had twice been sacked from the cabinet for breaking the ministerial code and had maintained a friendship with Jeffrey Epstein after he had been convicted of soliciting prostitution from a minor. We are left with the thought that maybe the reason Starmer never asked to see the vetting report was because he already suspected Peter Mandelson had failed.

Nothing about the story makes sense. Just supposing for a minute that the Downing Street version is true. That senior officials covered up the security vetting and approved Mandy’s appointment just because they thought that was what No 10 would like them to do. Putting their careers on the line for something that always had a high chance of being found out. The first rule of the Mandyverse: he always takes others down with him.

What was in it for the Foreign Office apparatchiks to be quite this dim? Or was their job just to tell the prime minister things he wanted to hear. “Don’t worry, Keir. When the president trashes you it’s a sign he really likes you. Just the negging of a consummate pickup artist.”

To imagine that everything happened exactly as Downing Street would have us believe does not just involve a collective suspension of reality. A journey into a parallel, hallucinogenic world where nothing is as it seems. It also means accepting that the people running the country are even more incompetent than we imagined. And that is a terrifying thought. That our politicians are nothing more than a bunch of chancers who have been winging it all along. So either Starmer misled parliament or he’s more useless than we thought. Neither position is sustainable.

Starmer, meanwhile, was in Paris to meet Emmanuel Macron for an online meeting of the Coalition of the Unwilling. Like-minded leaders who knew they ought to be seen to be doing something about the Iran war but didn’t really know what. Futile gestures all round. After all, it wasn’t as if any of them were in a position to make a difference.

Mid-morning, Starmer appeared in a park to give a short prepared piece to camera. “That I wasn’t told that Peter Mandelson had failed security vetting when he was appointed is staggering,” he began. Er, yes. But that you couldn’t even be bothered to ask to read the conclusion is even more staggering. Even if the whole thing was too much effort. There again, I suppose it was no biggy. Only the appointment of an ambassador to a US and a president with a narcissistic personality disorder.

Keir moved on. “That I wasn’t told that he had failed security vetting when I was telling parliament that due process had been followed is unforgivable.” How does he come up with such nonsense? The real question that Starmer can’t ask himself was why he was giving assurances to the Commons when he had no idea if they were true or not. He had just been living his best life. Reordering the world as he would like it to be. A prime minister who was not responsible for the words he was saying. Next he will be telling us he has been taken over by AI.

Then the piece de resistance. “Not only was I not told, no minister was told, and I’m absolutely furious about that.” Keir has spent a lot of time being furious recently. So much he doesn’t know. So much to know. If only there was someone in charge – a prime minister, say – who could make it their business to ensure civil servants kept ministers in the loop.

Talking of which … Starmer has said he only discovered his lordship had failed the vetting on Tuesday night. But somehow he never got round to telling his foreign secretary. It was only her department, I suppose. The first that Yvette Cooper knew of it was when the Guardian broke the story on Thursday afternoon. Left hand. Meet right hand. The same applied to Keir’s poor old chief secretary, Dazza. Jones too had been blissfully unaware. And if Keir really had been furious about being misled, he could have mentioned it at prime minister’s questions on Wednesday. Just saying. Truth, integrity and judgment matter. Just saying.

That just left Keir to say a few words – strictly no questions – at the end of the Iran summit. He was absolutely furious, he said. No one had told him Iran and the US had been at war. Yet more heads were going to roll at the Foreign Office for this. He was minded to make Olly Robbins resign all over again. Twice in two days. That would show him. He was also absolutely furious about the blockade of the strait of Hormuz. Civil servants had removed all maps of the Middle East from Downing Street without his knowledge and he hadn’t realised the strait was so narrow. Though the clue was in the name.

This, though, was about as good as it was going to get for Starmer. Back home the wagons were circling. Every opposition party leader was calling for him to resign. Worse, he had lost the country. Almost no one believes him. Even if he is telling the truth. Monday’s showdown in parliament will be box office. It could be Keir’s last stand.