Announcements by the United Kingdom prime minister outside the black front door of 10, Downing St are rare, and reserved for only the most important news. David Cameron used the platform last year to announce his resignation in the aftermath of the European Union referendum, and Theresa May appeared there the following day, after being elected Conservative Party leader, to sketch the priorities of her new government.

Yesterday morning she used it again — to reverse her formerly firm position that there would be no general election until the end of the term Cameron was elected for, 2015-2020. She will go to the polls on June 8, she says, in order to strengthen Britain’s negotiating position with the European Union.

“I have concluded that the only way to guarantee certainty and stability for the years ahead is to hold this election and seek your support for the decisions I must take,” she said, arguing that “the country is coming together, but Westminster is not.”

She has insisted in interviews since, that the decision was taken while walking in Wales, pondering the national interest.

But there is also the party’s interest. The fact that the Tories are a whopping 21 points ahead of a badly crippled Labour Party means, of course, that the Conservatives could be about to win a once-in-a-generation electoral monopoly. 

Conversely, on the basis that governments always lose popularity as they go on, had she not opted for an early election May could have faced a disaster in 2020: no one, after all, expects the next two years’ disentangling and re-engaging with the EU on new terms to be anything but a headache.

Had she waited until then it would have been the longest a prime minister had served without an election since Winston Churchill in World War II —  and he was afterwards voted out.

Whereas right now she has credibility. The post-Referendum period has been relatively smooth; the economy has not sunk; and her government has the legitimacy that comes from seeking to implement the wishes of the British people: the other parties, bar UKIP, were pro-Remain.

And she has every reason to want her own mandate. British politics is increasingly defined by the localism versus globalism dichotomy — the new left v. right —  that is reshaping the western political debate. It is present in Conservative disagreements over those who favor a “hard” versus a “soft” Brexit.

Sitting in the midst of this swirling internal tension is a prime minister who voted Remain but is committed to Brexit, who must hold together both her party and her country in the turbulent two years ahead as the UK charts a course that some are likening to its sixteenth-century break with Rome.

The idea was suggested recently in The Times by the Brexiteer Michael Gove, who described May as Britain’s first Catholic prime minister — Anglo-Catholic, of course. Arguing that “Britain’s path to preeminence in the past followed our break with Catholicism and embrace of the Reformation,” he said, Brexit too, was “once more freeing ourselves from a conformist continent to make our own way in the world.”

In this, he said, May was a reassuring and necessary figure because of her Anglo-Catholic ethic of service, attachment to traditions and unease with the wrenching pace of change brought about by globalization. These allowed her to identify with ordinary people outside the cities. But it also meant that she could resist some of the more buccaneering hard-Brexit, free-trade ideas within her government.

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It’s a delicate Anglican-type balancing act, and her party’s majority is almost as slim as Church of England congregations. Maybe she saw clearly from the Welsh hills of Snowdonia that she would need the greater political capital that comes with winning an election.

No one doubts she’ll win comfortably. The Labour Party under Jeremy Corbyn is unelectable, and even his supporters despair of the chaos he has wrought on the party; the Conservatives are set to take a large number of its seats in the working-class but pro-Brexit north and west. UKIP, the original Brexit party, is in similar meltdown, and voters no longer see its point.

The only party set to make some gains are the Liberal Democrats, especially in the south-west and Remain-supporting areas. Having been almost wiped out in 2015, under their new evangelical Christian, pro-EU leader, Tim Farron, they are pitching for the young, urban voters who feel frustrated at the UK’s new direction.

Then there’s the tiger of Scottish nationalism, newly roaring since the EU referendum in which they voted Remain by a thumping majority.

The Scottish Nationalist Party (SNP), who want a new referendum on independence in 2019, have so far been turned down by the prime minister. May has insisted that no second referendum will be possible until after Brexit in 2020, but if the SNP increases their majority in June, it will get harder for her to maintain her refusal without inflaming nationalist sentiment.

Conversely, if May takes seats from the SNP in June, it will dampen enthusiasm for a referendum. 

Northern Ireland, too, is in an uncertain place following the collapse of the power-sharing government and fears over a new hard border between the north and the Republic of Ireland following Brexit. The north voted to Remain, but Catholics in far greater numbers than Protestants. A return to sectarian polarization over the national question is set to reappear in June’s election, even if no one expects a return to violence. 

The prime minister is framing the election as an us-versus-them plebiscite on leadership, “a choice between strong and stable leadership in the national interest, with me as your prime minister, or weak and unstable coalition government, led by Jeremy Corbyn, propped up by the Liberal Democrats, who want to reopen the divisions of the referendum, and Nicola Sturgeon and the SNP.”

Her case, therefore, is that “every vote for the Conservatives will make me stronger when I negotiate for Britain with the prime ministers, presidents and chancellors of the European Union.”

Yet to frame this as a choice between unstable, coalition government or a strong Conservative government is unconvincing. No one doubts that the Conservatives will win handsomely, and be able to form a strong government. 

And there’s the rub for May. It is not clear that voters will accept her argument that a failure to vote for her will weaken the UK’s negotiating position.

If many Remain voters — 48 per cent of the country — believe the government is being dragged down a hard-Brexit route that will leave the UK significantly isolated and weakened in the world, they will reach for the opposite conclusion, that by voting Labour or Liberal-Democrat, they will still end up with a Conservative government but one that will be forced to listen to those in her party who want a close and constructive relationship with Brussels. 

Maybe voters will actually vote on her manifesto. The election allows May to ditch Cameron’s election pledges and create her own policies, ones she will argue must be driven by post-Referendum realities.

The bishops of England and Wales and Scotland will want to focus on those pledges in their pre-election advice to voters, which they must draw up quickly in order to shape the campaign season.

Expect the usual on immigration, life issues, euthanasia, the environment, prison reform, and concerns about the effects on poor families of cuts to social security.

This time, though, the bishops will need to address Brexit — a subject they carefully avoided on the eve of last year’s referendum — or be seen as out of touch with the moment. They will, of course, carefully avoid sounding like ‘Remoaners,’ and accept the UK’s direction of travel as an opportunity.

But my guess is they’ll issue a challenge. They’ll want to ask the British people to consider what values they want the UK to represent in an increasingly polarized world, and warn against the risks of withdrawing from the world stage into a mythical self-sufficiency underpinned by nationalist resentment.

It’s the kind of thing the pope should have warned Henry VIII about in 1531.