Curiously enough, considering the avalanche of criticism about the endless delays, it turns out that the publication of the Chilcot report could not be better timed.

This is entirely accidental, of course. Whenever it was that Sir John and his colleagues began (top dendrochronologists plump for 1872), their intent was not to delay until the aftermath of an EU referendum which had yet to be mooted.

Whether through pure chance or an impressive instance of Jungian synchronicity, the two events coalesce to tell us this: in the dozen years between one Prime Minister making the worst foreign policy mistake in British history and another committing the worst domestic policy mistake the UK has ever seen, nothing – absolutely nothing – was learned.

The similarities between these twin catastrophes are overwhelming, focusing a dazzling spotlight on the failure to learn from experience that underpins the infantile inadequacy of our early millennial political leadership. With Iraq, a PM with a messiah complex had such misguided faith in his limitless powers of persuasion that he took a suicidally reckless gamble. Ditto with David Cameron and the referendum.

Just as Blair presumed his silver tongue would seduce the UN into backing that legality-conferring second resolution, Cameron blithely expected to charm fellow European leaders into doing his will. As Andrew Marr put it: “Cameron believed that he could negotiate a deal with his EU partners so good that he would win a subsequent referendum… a huge miscalculation.” Ya think?

Blair propelled us into Baghdad via a House of Commons vote which seemed a legitimate expression of the democratic will then; but which, since it was won with claims (about weapons of mass destruction) subsequently revealed as false, was nothing of the kind. Similarly, the legitimacy of the Brexit victory is already ridiculed by admissions that the pivotal assertions about migration control and increased NHS spending tended towards the fanciful.

Neither con trick perpetrated against the UK electorate could have been pulled off without Rupert Murdoch as a partner in the grift. Had The Sun not slavishly peddled the invasion of Iraq, megaphoning the “45 minutes from Armageddon” claim, it would have been politically impossible. Had that same journal of record, with the rest of the reactionary press, not appealed to the worst in us by placing immigration at the heart of the campaign, Remain would surely have won.

Perhaps the most dismal point of comparison is this. While we may argue about the legality of the Iraq invasion, no one disputes that Blair’s touching loyalty to George W Bush extended to joining his cabal of White House gangsters in declining to worry about anything as trivial as post-war planning. A cameo from early 2003 found Dubya’s father, the elder President George HW “Pappy” Bush, wandering bemusedly around Camp David muttering, “What about an exit strategy? Why haven’t they got an exit strategy?” in that beguilingly Jack Nicholsonesque voice of his.

No exit plan then, no Brexit plan now. Nothing was learned from Iraq about the paramount need for detailed contingency planning.

Those on both sides of the referendum divide spent years observing the results of the Anglo-American alliance’s deafness to impeccably accurate warnings about how the situation would develop, and nothing sank in. Blair was told that any ensuing power vacuum would be filled by a Sunni versus Shia civil war. He was told this would embolden Iran, making it a regional superpower. He was told that, far from “making this country safer” as he so glibly claimed, it would bolster the recruitment of suicidal terrorists here and elsewhere. How could it not? And he was told that it would gravely destabilise a region which was hardly a paradigm of stability in the first place.

Caricaturing these warnings and others as the bleatings of “Saddam apologists,” he gaily sashayed into Iraq with no regard to the consequences once the tyrant had fallen. And 13 years on – with each of those warnings having come to pass – we see the same dearth of planning from the political class once again.

On no side of the Tory EU divide did anyone – not Cameron and Osborne, not Johnson and Gove – prepare for the highly unlikely event, as it struck the terminally smug until about 11.30pm on June 23, that the UK voted Out.

This criminally amateurish approach to moments of defining importance refines Marx’s over-quoted saw. Here we find history repeating itself: the first time as tragedy, the second as tragedy.

Each episode, that said, has had its farcical flourishes. Tony Blair insisting that the bombings of July 2005 had nothing whatever to do with Iraq; leading Brexiteers boldly confessing within hours of their triumph that there wouldn’t be an extra £350m a week for the NHS after all. But no one seemed to find either wildly amusing.

Without Iraq, there would be no Brexit. The Arab Spring that led to the Arab Conflagration would not have happened. Isis would not have developed into the menace it is. The exodus of refugees would not have flowed to Europe, Nigel Farage could not have released his poster of Syrians on the Slovenian border, and the cynical fear-stoking that won the referendum would not have worked as it did.

Chilcot report: Tony Blair made fully aware of post-Saddam chaos risk in Iraq but went to war anyway

Yet the impact of Iraq on our EU membership goes deeper than that. If the British public’s reflexive distrust of establishment politicians came into riotous bloom on 23 June, Tony Blair sowed the seed in 2003. Whether he lied, exaggerated or engaged in wilful blindness to ignore the glaring caveats about the WMD intelligence, he devalued the currency of credibility far more dramatically than Brexit has devalued the pound. He rendered the prime ministerial warning literally less than worthless. He made it a positive advantage for the other side.

Having closely observed the horrors that followed the removal of one tyrant without effective planning for the consequent void, David Cameron expertly replicated that to visit the hell of Iron Libya. Lest that didn’t do enough to inscribe the epitaph ‘Heir to Blair ‘on his political tombstone, he then indulged his epically misplaced self-confidence by calling an entirely needless referendum.

Sir John Chilcot has said that he hopes his report will help to avoid future calamities of the kind. Good luck to him with that.