The Prime Minister spent Thursday at the World Economic Forum in the Swiss Alps. But she may have another mountain to climb back in Westminster: persuading her backbenchers to stay on Team Theresa.

The 1922 Committee

There are two ways to trigger a leadership contest: either the current leader resigns, or 15 per cent of Conservative MPs write to the chair of the 1992 Committee of Tory backbench MPs saying they no longer have confidence in the leader.

A confidence vote follows. If the leader fails to get a majority of votes, he or she resigns and cannot stand in the subsequent election.

The Conservatives currently have 316 MPs in the Commons. So if 48 of them write to the head of the Committee, Graham Brady, then Theresa May will have a fight on her hands.

The Sun reported yesterday, quoting anonymous sources, that Mr Brady could have received at least 30 letters already and has “begged” MPs to “be careful” about adding to his inbox. Today the paper reports that “it is believed that he has already been sent at least 40 – meaning that just eight more letters would force him to call a poll of all Tory MPs.”

What next?

If that magic 48 threshold is passed, and the leader loses the confidence vote, the next step is a series of ballots in which Conservative MPs vote for their preferred candidate. At each stage, the candidate with the fewest votes is eliminated, until the top two remain.

The last leadership election, which took place in the post-referendum blur of July 2016, saw five candidates thrash it out over two ballots of Tory MPs. There would have been more votes, but Stephen Crabb dropped out between the first and second round.

Once the parliamentary party has picked its two preferred candidates, it’s over to the rank and file party membership to choose the leader on a “one member, one vote” basis.

In the last contest, this was supposed to have seen Theresa May and Andrea Leadsom compete on 9 September 2016, but Mrs Leadsom dropped out before the ballot could take place, installing Mrs May as leader.

While this fast-tracked her to Number 10, some commentators have suggested that bypassing the party membership was unhelpful for Mrs May in the long-run. Top Conservative donor Alexander Temerko said recently that “it is important to elect [the next] leader by way of democratic vote with no coronation or other tricky methods.”