A crucial day for Theresa May

After one failed coup, Tory Brexiteers weren't going to miss again.

Sir Graham Brady announced this morning that the 48 letters had been breached - meaning the prime minister was now facing a vote of confidence.

She had hoped to avoid this showdown by pulling the Meaningful Vote on her Brexit deal as she raced to The Hague, to Berlin and to Brussels to win further concessions on the thorny issue of the backstop.

:: May: I will contest confidence vote with everything I've got

But events have overtaken her and tonight will be the moment of reckoning as MPs deliver their verdict on her leadership.

MPs are split on whether she will survive the vote: loyalists are certain the bulk of her party will back her, but Brexiteers say the mood has hardened against her and her government - without the support of the DUP - has hit the buffers.

It will be a crucial moment for her as she heads to that secret ballot of Tory MPs.

:: MPs reveal whether they support or oppose PM

She has the rest of the day to convince 158 of them to stick with her in that vote and will enter her final plea at the 1922 meeting at 5.30pm, just minutes before the ballot opens.

Fighting now for her political survival, the prime minister was defiant outside No 10 this morning, as she told her MPs she "will contest that vote with everything I've got" and warned wavering Brexiteers that ousting her could result in their precious Brexit not happening at all.

Her cabinet have publicly rowed in behind her, but this is a secret ballot and she cannot know if she can win.

If she does, MPs cannot call another vote for 12 months and she will claim victory, demand the party fall in behind her and try to press on with her Brexit plan, emboldened.

To do that convincingly, she'll have to win by a big margin.

If she loses, Britain will have a new prime minister in the new year, likely a Brexiteer given that it is the hugely eurosceptic party membership who have the final say in who should be leader.

All the while the Brexit clock is ticking down with just 108 days until Britain quits the EU and the Tory party are more divided over the manner in which we leave now than it has been since the 2016 referendum.

The ballot tonight will not change this incontrovertible fact. But it's a showdown between two wings of the party that needs to play out if the Tories are to have any hope of deciding where to go next with Brexit

:: The confidence ballot takes place between 6pm and 8pm tonight, with the result at 9pm. Follow live on Sky News