She’s no longer in No 10, but we haven’t seen the last of Theresa May

Though history may well treat her more kindly, Theresa May seems, for now, destined to be written off as one of Britain’s very worst prime ministers.

She is, as we see, the universal scapegoat for the failures of Brexit. She had, as the popular phrase goes, “one job” (ie deliver Britain out of the EU) and she botched it. Her critics, opponents and enemies on every side of politics and in every part of the kingdom, after a few courtesies, are kicking her when she’s down.

Still, there is reason to believe that she may end up as Britain’s greatest ex-prime minister. Despite her well-known type-1 diabetes, she is hardly past it at 62 years of age. If the past few years prove anything it is that she possesses a rare fortitude, stamina and strength of character often lacking in those who have tormented her for too long. Some of them are not fit to lick her kitten heels, you might say.

She is not going in disgrace, or even failure, in her view, and must see no reason to do a Captain Oates. She is, though, concerned about her “legacy”, hence her hurried spending spree in recent weeks.

She is a politician, and enjoys it. She is a public servant, and enjoys that too. She has said she is staying in the House of Commons, not clearing out as fast as possible with an ill-disguised contempt for the place (unlike Tony Blair and David Cameron). You can accuse her of as much hypocrisy as you like, not least because of her record at the Home Office (“hostile environment” regime) and supporting the austerity programme of the governments she served in and headed; but she still believes in things. When she came to power in 2016, and made her now highly poignant speech in Downing Street about “burning injustices”, she seemed to mean it. I think she did.

Nor do you have to look very hard to see the particular causes she cares about. Mental health, especially among the young, is something she talked about whilst in office. No, the funding was never going to be good enough for some, but she (and Jeremy Hunt) made some progress on the issue.

She has also devoted much effort to fighting modern slavery. We all saw the appalling case this month of the eight modern slave masters convicted of trafficking 450 Poles to the UK on the promise of a better life, only to then harvest virtually all of their minimum wage pay packets and benefits – some £2m.

Their conviction demonstrates the scale and horror of this contemporary social evil. As home secretary, May pushed through the 2015 Modern Slavery Act. This was the world’s first such legislation, and it is an achievement that May should be rightly proud of. It isn’t the kind of thing that entertains the gossips of Westminster, or would fill the front page of a tabloid newspaper, but it was – and is – an important landmark.

To judge her long-term commitment, this is what May said about it in 2016: “These crimes must be stopped and the victims of modern slavery must go free. This is the great human rights issue of our time, and as prime minister I am determined that we will make it a national and international mission to rid our world of this barbaric evil.

“Just as it was Britain that took an historic stand to ban slavery two centuries ago, so Britain will once again lead the way in defeating modern slavery and preserving the freedoms and values that have defined our country for generations.”

Theresa May, then, as a modern-day William Wilberforce. With an international profile and that indefatigable spirit of hers, I don’t see why not.

She’d need money. May doesn’t seem the money-grabbing type, but if she wants to do something more than make speeches and turn up for panels with Bill Gates at Davos, then she’ll need to do the modern ex-prime ministerial thing and charge fees for appearances and “consultancy”, and set up a foundation, something with a preferably charitable structure and purpose. There are many precedents. The Thatcher Foundation, for example, devoted itself to exporting free-market liberal and democratic values around the world. Tony Blair’s internationally focused work was in tandem with his role as a Middle East peace envoy and the slightly absurdly named Tony Blair Associates, which sounded like a showbiz variety agency, providing strategic advice to anyone who wants it (not always paragons of human rights), with the fees going to his worthy activities. These included the Tony Blair Sports Foundation, the Tony Blair Faith Foundation and, currently, the Tony Blair Institute for Change, which “aims to help make globalisation work for the many, not the few. We do this by helping countries, their people and their governments address some of the most difficult challenges in the world today.” It makes up in ambition what it lacks in precision.

Sarah and Gordon Brown devote themselves to the cause of global education, including Brown’s role as United Nations Special Envoy for Global Education.

The downside of such work is that you get ridiculed for the sometimes obscene fees for speeches and the like, and the grandiosity of your publicity makes you look like a bit of a Walter Mitty. The upside is that you keep yourself occupied and get to do some good in the world. For the vicar's daughter Theresa May, that must be a calling.

In Tony Blair’s case these causes have provided some partial distraction from the Chilcot Inquiry, the never-ending Iraq war controversy and allegations of war crimes.

It is rare, indeed, for prime ministers to entirely slink away. Only a truly calamitous end to your time in office leads to an afterlife lived in relative obscurity. Like David Cameron. In the inimitable words of Danny Dyer on Good Evening Britain last year: “So what’s happened to that t*** David Cameron who called it on?

“How comes he can scuttle off?” Dyer demanded to know. “He called all this on. Where is he? He’s in Europe, in Nice, with his trotters up, yeah, where is the geezer? I think he should be held account for it.” Unwisely, Cameron had himself been chillaxing in his £25,000 “shepherd’s hut”, the very picture of post-referendum insouciance. It may be some small consolation to May that Cameron’s reputation will remain sunk while hers will recover.

May will, like every other ex-PM, have another cause more personal – defending their record. A volume of memoirs is one weapon, though it tends to signal that you’ve said goodbye to the chance of any future high office. May will, above all, want to defend her deal and may soon get the opportunity to say to the Conservative critics of her withdrawal agreement, and Prime Minister Johnson: “I told you so.” She might especially enjoy watching Boris lose a vote of confidence and getting chucked out by Christmas.

Nearly every ex-prime minister has been unable to resist the temptation to interfere in the activities of their successor. Margaret Thatcher was the ultimate back-seat driver, leading a rebellion against her successor John Major’s centrepiece legislation on Europe, the Maastricht Treaty (from whence much of today’s rabid Tory Euroscepticism derives). Ted Heath spent another 37 years in the House of Commons after he lost the 1974 general election and the party leadership shortly after. He sniped, sneered and growled at everyone who followed him as Conservative leader for the ensuing decades: the “Incredible Sulk” as it was called. James Callaghan, ex-Labour PM, attacked his own party’s defence policy at the 1983 election; Harold Macmillan, at the age of 91, famously warned Thatcher off privatisation (“like selling the family silver”), and, now, John Major threatens to take Boris Johnson to court if he suspends parliament to get Brexit through. Blair, Brown and Major have all been prominent critics of May, advocates of Remain and a second referendum.

May will certainly resist, for example, a no-deal Brexit and suspending parliament with all the authority she can muster. She will be listened to, as the only ex-PM in the house. She won’t stay silent.

So the notion of any easy, relaxed retirement by the pool or walking the Welsh hills is something of a myth. As a young executive at the Bank of England in the late 1970s, interestingly, May was seconded to the (Harold) Wilson Committee on reform of the City of London, a rare example of a future PM working for a retired one in such a way. So she knows that ex-PMs can be put to some use.

Wilson’s retirement was increasingly marred by frailty and he did, sadly, fade from public view. If her heath and spirit holds up, May can look forward to a far longer and far more successful post-premiership than her turbulent and disappointing three and a bit years in No 10. The closest analogy would in fact be Jimmy Carter. Since his one-term presidency collapsed in failure in 1980, the Jimmy Carter Foundation has performed outstanding work in human rights, peace making and disease eradication – a fine model for any ex-national leader.

Good luck to Theresa May; she deserves a bit of good fortune.