It's worth remembering how uncompromising it was. Britain's best-selling Sun newspaper dwelt on her threat to withdraw security cooperation with the EU, if Brussels didn't give Britain a favorable exit deal. "PM's Brexit Threat to EU: Your Money or Your Lives," screamed the headline.
But then she called the election to win a mandate to take back control of "our laws, our borders and our money" -- and lost.
Instead of basking in triumph at Downing Street, she now clings to power because her party, like her country, is split down the middle. Her own Chancellor (finance minister) and Home Secretary, to say nothing of the civil service, wholly oppose her policy, but are too weak to change it either.
Too weak -- but not silent. Philip Hammond, the Chancellor, told an audience of ultramontane globalists at Davos that he hoped to make only "modest changes" to Britain's relationship with the EU.
But this has given Brexiteers the right to ask what's the point of going to all the trouble of leaving the EU, only to end up with "modest changes"?
Whatever happened to what is, after all, UK government policy of taking back control of borders, laws and money? What if it wasn't just her belligerent language on security that had been replaced by a far wiser unconditional guarantee to come to Europe's military aid? What if her whole Brexit policy was coming unstuck? The Brexiteers had to make their presence felt before it was too late.
If the Chancellor's intervention provided the pretext, the EU's own negotiation guidelines provide the real reason: Brexit will take time to implement, and this has given rise to the notion of a "transition period." The term's a misnomer. Everyone has always known that far from a smooth gradation towards Brexit, it is just a delay of most of its effects.
The EU is prepared to grant Britain a so-called transition -- but on the condition that EU law continues to apply to the UK while it goes on and Britain does not get a vote in European institutions. Brexiteers have finally decided that this, which had been acceptable to them this summer, is now a concession too far.
It would, said anti-European leader Jacob Rees-Mogg, a man whose effete demeanor disguises fanaticism of Cromwellian intensity, render Britain a "vassal state."
The hardliners are afraid their country would end up in a gilded cage. By keeping disruption to a minimum, it would prove far too convenient to extend such a status indefinitely (they overlook that the EU itself has said it can't go beyond 2020). This Eunuch Brexit, which was supposed to make Britons tough and free, would have achieved the exact opposite.
Hammond's unguarded remarks gave the hardliners an excuse to launch their latest rising.
The instrument this time was Graham Brady, the MP who chairs the Conservative backbench group the 1922 committee and must trigger a vote of confidence in the Prime Minister if he receives 48 letters from Tory MPs saying they would like one.
Pretending he was concerned for her safety -- but obviously communicating the reverse -- he let it be known that the number was awfully close to the threshold. Nice leadership you've got there, shame if anything would happen to it. Can I interest you in some Brexit insurance, Madam?
Still, this Brexit mob has been living off the reputation it gained in the 1990s, when it subjected then Prime Minister John Major's government to legislative guerrilla warfare.
The current crop are, by comparison, soft. They plead loyalty to the Prime Minister. They have accepted concessions on everything from Northern Ireland to budget contributions and even the role of the European Court of Justice in overseeing elements of British law that they had previously insisted were unthinkable.
The rules to replace a Conservative leader -- who at the moment is also the Prime Minister -- eventually work in the hardliners' favor. The final decision is made by party members, who will vote for the most pro-Brexit of candidates.
But before that they have to win the vote of no confidence in the incumbent. There's every risk that they would lose it, and be left with their worst nightmare -- a weak prime minister hostage not to them, but to the MPs who voted remain and favor a softer Brexit.
The hardliners need her to resign before the confidence vote can take place, and for that they need some of her cabinet ministers to walk out. The ministers will have to do so under the shadow of the ancient rule of leadership contests: He who wields the dagger never wears the crown.
If they are to remove May, at least two cabinet ministers will have to sacrifice their ambitions to replace her. Unless they discover such courage, May will keep going, as though she herself were one of Margaret Thatcher's policy programs: Because there is no alternative.