Few politicians are introverts – let alone senior ones; let alone Prime Ministers. But such is the disposition of Theresa May – or at least, if not precisely an introvert, she is unusually at ease with silence, as a mass of accounts of dealing with her verify. This sense of solitude, modulated by a happy marriage, almost defines her. Who can pin down what shaped it? But part of the answer must surely lies in her upbringing as an only child, with a clergyman father driven by an persistent commitment to public service.

But despite this clear-cut character, there have been not so much one, but three Theresa Mays, as far as her political career has been concerned. The first was a cautious moderniser: an industrious, capable woman on the Conservative benches at a time when these were rarer than they are now. Given the lack of competition, and her own clear sense of duty, she rose fast – becoming the Tory Chairman who warned activists that theirs was seen as “the Nasty Party”.

The second May saw her find an adviser and gain a department. The former was Nick Timothy, whose Conservative profile was unusual and distinctive – left-leaning on the economy, right-looking on social policy (when it comes to immigration control, anyway). The latter was the Home Office, whose culture of command, wariness and control reinforced her own instincts. She began to make leadership pitches, the first to a conference held by this site, with a distinctly interventionist flavour.

In the aftermath of the EU referendum, she become literally the last woman standing, after the withdrawal from a 2016 leadership contest of Andrea Leadsom. To many Party members, she looked more than capable of resolving its post-plebiscite tensions. She had been a Remainer, but had deliberately distanched herself from George Osborne’s “Project Fear”. Her Home Office record was mixed, but she had fought the former Chancellor, and others, over migration control. She appeared to offer grown-up government after a decade or so of Blair-light spin.

This site was enthusastic about the possibilities a May premiership offered and, at first, our optimism was more than justified, as she announced a Brexit commitment to take Britain out of the EU’s insitutions altogether – the most natural way of intepreting the referendum result. Then came the 2017 election gamble and Timothy’s manifesto over-reach. May’s majority vanished. So did Timothy. Enter her third and final manifestion. During it, the social conservatism, such as it was, seemed to vanish, leaving a Government leaning left both socially and econimally.

The Conservative Party is still picking up the pieces, as this leadership election has demonstrated – dispossessed as the party is of the economic thinking that ran through Thatcherism all the way to “austerity”. But it was on EU policy that May Mark Three – in so many ways a reversion to type – became most evident. In retrospect, it is evident that she was hostile to No Deal; even at the time, it was clear that she was incapable or unwilling of seeing Brexit as an opportunity rather than a problem; and the Timothy-era clarity of purpose was replaced by the splitting of differences.

May’s supporters claim that she had no choice but to do so, given the depth of division within the Party over alignment and diversion, and deal or no deal (if necessary). There is force in the argument, but also strength in the counter-case – principally, that her Government treated Ireland with a chacteristically English complacency; failed to spot the constitutional and political traps in the original backstop, and would have stood a good chance, had it not folded early on the proposal and fought instead for a compromise, of getting a deal through Parliament.

Instead, May gradually ceded ground to the point where she lost the trust of both sides of her Parliamentay Party simultaneously – on transition migration, transition extension, a regulatory border in the Irish Sea, even on the Customs Union, at least as far as the revised, all-UK backstop was concerned. And as the referendum receded over time, the Remain-sympathetic Commons grew bolder – with the Grieve-Cooper-Letwin push for indicative votes and extension. The more centralised her decision-making became, the less control over events she actually had.

Perhaps we all eventually turn into caricatures of ourselves. As time went on, May certainly appeared to. That childhood-learned sense of duty seemed to narrow to a resolve to cling on in office; the commitment to others, a conviction that the country needed her. The game was clearly up by mid-March, when MPs crushed the Withdrawal Agreement for the second time and a vote on extension was announced. The Conservatives’ poll ratings began to fold that week. These have not reached 40 per cent since.

If you promise over 100 times that Britain will leave the EU on March 29, and it doesn’t; then say that you are not prepared to delay Brexit later than the end of June, but do; announce that it would be “unacceptable” for European elections to take place, but they happen; and if you denounce Jeremy Corbyn as a threat to the country, but then seek to work with him over Brexit, you will poison the well not only for yourself, but also for your party. Conservative MPs opted for Boris Johnson for simple, sole reason that they think he has the best chance of cleansing the waters.

May joined the Conservative Party as a teenager. She married it, so to speak: Philip May was also a young Tory activist, and could well have become an MP himself. There is a terrible irony in this long-time Party member, a former Conservative councillor who is “one of us”, having presided over an attempt to work with a hard-left Marxist. You may say that she had no choice, given what the “Spartans” did to her deal, third time round. And that she could not have ultimately have prevented extension, at least if her government was not to fall.

To which the response must be: if that last claim is true – and we suspect it is – she should have quit mid-March, telling the voters that, since the Commons was thwarting her Brexit promises, she would go. Yet she hung on – though doing so didn’t save her in the end, as was evident at the time. Perhaps the best explanation is that she really was set on staying in Downing Street longer than Gordon Brown. Or, more straightforwardly, that it is a rare Prime Minister who leaves voluntarily – only Harold Wilson in modern times, and he was ill.

Having been so hopeful about May during the Timothy era, we would like something to salvage from the wreckage. There are floating chunks of woodwork – the small business rates cut; parental bereavement leave; the push against modern slavery. But the loss of even a small majority left her Ministers all at sea. And the centrepiece of May’s legacy bid is an emissions commitment that won her pleasing headlines, but leaves her successors a delivery headache. The loner has ended all but isolated, and maybe the key to the second is in the first.