We know Halloween is overhyped, but it did promise to be genuinely terrifying this year. Jacob Rees-Mogg warned that the Conservative party would cease to exist. Boris Johnson declared that he would die in a ditch. Mark Francois informed daytime television viewers that the country would explode. In the end, the day’s most dramatic event was a row about handshaking between Sajid Javid and Hugh Grant.

I speak, of course, of the third Brexit extension. Just as we did not leave the EU on 29 March, or on the second deadline of 12 April, we will not leave on 31 October. Incredibly, staying in the EU beyond an entirely arbitrary deadline did not prove especially frightening after all. The Tory Nostradamuses’ fears (or secret hopes) of social and political chaos came to nothing. Life after the latest missed deadline will continue exactly as before.

It is, of course, amusing that Johnson’s hyperbolic threats have been so definitively exposed. But there is a serious point. Imagine any other prime minister making one single, existential pledge in order to reach office, and then again upon entering it. Imagine that prime minister repeating the sole pledge each day for three months. Imagine him saying he’d die for it. And then imagine him breaking that pledge, openly and unambiguously, and moving on as though nothing had happened. A leader with honour or integrity would resign.

It is worth recalling the genesis of the 31 October Brexit deadline. Theresa May’s similarly arbitrary date of 29 March, to which she too clung, was at least decided in Downing Street. The 31 October cut-off was a compromise devised by the 27 other EU member states while May waited outside the room.

It was a symbol not of taking back control but giving it away. And yet the Brexiters endowed it with more national mythology than the ravens at the Tower of London. The date’s rapid fetishisation embodied how Brexit had been permanently transported from the prosaic realm of jobs and trade figures to an epochal quest of romantic nationalism.

Nobody was more instrumental in formalising this association than Johnson. It was the only issue that distinguished him from Jeremy Hunt during the Conservative leadership contest. Hunt said he would be prepared to extend for a few weeks beyond October if it meant signing a deal. Johnson declared that he would rather undergo the chaos of no deal at all. The future of an apparently serious country was to rest on the immutability of a single date. The date won.

But of course Johnson underestimated parliament from the start. It would not allow him to take us out of the EU with no deal. The prime minister in turn became so transfixed by no deal that by the time he caved in to the EU on the customs border in the Irish Sea, it was too late to meet his deadline. He secured his deal, but attempted to ram it through parliament in just three days – less than was allocated to the Wild Animals in Circuses Act. The only reason to fast-track the most significant legislation of modern times was to spare Johnson the embarrassment of extending Brexit by even a couple of days.

The Tories will now spend the next six weeks alternatively ignoring the broken deadline and blaming parliament for forcing an extension. We must challenge that narrative. The 31 October deadline is not a sideshow. It goes to the crux of who our leader is and what he represents.

First, a government entrusted to look after our welfare was more interested in one man’s rhetorical ditch than millions of people’s actual livelihoods. Ministers attempted to deny a vital bill scrutiny in order to protect the prime minister’s ego. Their contempt is so normalised that we no longer even notice it.

Second, Johnson is incapable of taking responsibility for his own actions. He did not say “we will leave the EU on 31 October if parliament or Jeremy Corbyn permits it”. He guaranteed that date, “no ifs, no buts”, do or die. Further, he knew from the beginning that the parliamentary arithmetic would stop a no deal departure on 31 October, but he repeated his grand promise over and over.

Third, and most important, the missed deadline illuminates our new political culture. Johnson made a pledge he knew he could not keep. He continued to make it long after it became obvious he would not keep it. He was still promising to honour it late last week. By any normal standards that revealed his profound delusion, dishonesty and weakness.

Yet his party and the rightwing media offered him no serious challenge or rebuke. It is not just that he can lie with impunity. It is not even that his dishonesty is “priced in” and we expect him to lie. It is in fact much worse: we want him to lie to us. It is central to his appeal.

Here, then, is the truth. Halloween will not scare us this year, because we never need to be afraid of staying in the EU. Life will stay the same on 1 November and continue on even if we never leave. But everyone should now see that our prime minister governs not in the interests of the nation, or even his party, but himself alone – and that truly is frightening.

• Jonathan Lis is deputy director of the thinktank British Influence