The most disastrous premiership since Neville Chamberlain is about to draw to a brutally abrupt end. David Cameron is a failure on his own terms, as well as the terms of his opponents. The historical revisionists will one day come and – for the sake of contrarianism – try to salvage Cameron from a wreckage of his own making. Don’t bother.

As he gathers his belongings from No 10, I wonder if he has the occasional flashback to the conference speech in 2005 that secured him victory over the Tory leadership frontrunner, David Davis. It was soaring rhetoric infused with optimism: “And let’s resolve here, at this conference, when we put defeat behind us, failure behind us, to look ourselves in the eye and say: never, ever again.” Perhaps he lingers on the memory of winning a majority last year that the pollsters and bookies declared was near impossible. “There was a brief moment when I thought it was all a dream,” he would later say. “I thought I had died and gone to heaven.” It must seem like a dream now: one from which he would prefer to wake.

Cameron crept into government in 2010 promising to eradicate the deficit in a single parliamentary term. His government didn’t even come close. His government was “paying down Britain’s debts”, he declared in 2013: it actually added more debt than every Labour government put together. Upon assuming office, he committed “to ensuring our whole country shares in rising prosperity”: his government presided over the longest fall in wages and the most protracted economic stagnation for generations. After the last general election, his chancellor introduced three fiscal rules: a welfare cap, a national debt falling as a proportion of GDP, and a budget surplus by 2020. The first two were broken by March; the budget surplus was ignominiously abandoned by George Osborne at the beginning of July.

Osborne himself was less consistent on austerity than his supporters or his critics (like me) have often admitted. But his potential successors now call for his economic strategy to be abandoned, a confession of failure. His business secretary, Sajid Javid, advocates a fiscal stimulus that could mean raising the deficit from 3% to 5% of GDP. All that misery; all that stagnation; all that bloodcurdling rhetoric about the disastrous consequences of Britain not cutting its deficit. All for what?

And take another linchpin of Cameron’s domestic agenda: education. “We’ve got to win the great debate about education in this country, to give choice to parents, freedom to schools, and to fight for high standards,” he declared back in that 2005 speech. A recent league table revealed that local authority schools are, overall, outperforming the government’s flagship academies.

There is an exception: equal marriage for same-sex couples, won on the backs of Labour and Lib Dem votes. What a tragedy that a rare shining achievement is one that some have alleged he regretted.

Cameron hoped that his premiership would preserve the union for generations. But Scotland’s independence referendum result was not only far narrower than anticipated, it left the country polarised and halfway out. While the Scottish National party only had six MPs when David Cameron came to power, he stands down facing a parliamentary bloc of 56 nationalists. With Scotland ejected from the EU against its will, it has never looked more likely to leave and precipitate the breakup of the UK.

What of foreign policy? Little is said about David Cameron’s major foreign military escapade: war in Libya. Rather than ushering in a peaceful, stable, democratic Libya, the country was left consumed in chaos, war and extremism.

And then his means of political suicide: the EU referendum. It was called not with the national interest in mind, but as a method of resolving internal party divisions. It helped secure him a majority, and he gambled everything on it. The man who wanted his party to stop “banging on about Europe” lost, and was left personally repudiated, his country plunged into its worst crisis since the war: economic turmoil, a wave of xenophobia and racism, and a country more bitterly divided than it has been for generations. Those who voted remain resent him for being the instrument of Britain’s exit from the EU; those who voted leave resent him for what they regard as scaremongering.

Cameron leaves Downing Street with few admirers, a country in crisis, the central aims of his premiership in rubble. It is nearly enough to make you pity him – but, given how grave the situation facing our country is, not quite. His premiership is a tragedy for which we will all pay.