How is a Tory leadership contest triggered?

It takes 48 Conservative MPs to back a no-confidence vote in Theresa May to trigger a leadership contest, according to party rules. That has now happened.

A leadership contest can be triggered in two ways.

The first way is if the leader of the party resigns. If they do not but MPs are unhappy with their leadership, 15 per cent of Conservative MPs must write to Sir Graham Brady, the chairman of the 1922 Committee of backbench Tories. The party has 317 MPs, so 48 letters were needed.

What happens when a contest is triggered?

Mr Brady informs the prime minister and the chief whip directly. The vote will be held between 6pm and 9pm on Wednesday and the result should be known by 10pm.

How many MPs would need to vote against May to remove her?

A simple majority of 159 MPs could oust Mrs May, though the leader could decide to resign if she received a significant number of no-confidence votes.

How do we know how many letters there are?

No one knows how many letters have been sent, apart from Mr Brady. We know it is at least 48 but Mr Brady on Wednesday declined to say how many there were.

What happens if Mrs May wins?

Should Mrs May defeat her critics, they would not be permitted to challenge her for another year.

What happens if Mrs May loses?

There will be a leadership contest to decide her replacement. Her replacement will become prime minister, but a general election will not automatically be triggered. If several candidates come forward, a secret vote is held among Conservative MPs to whittle down the field. The candidate with the fewest votes is removed and Conservative politicians vote again.

Then the process is repeated, on Tuesdays and Thursdays, until only two candidates remain. These two candidates are then put to a postal ballot of the wider Conservative Party membership.

Participants need to have been party members for more than three months. When David Cameron decided to step down as prime minister and Conservative leader after the EU referendum in 2016, five candidates came forward. The field was narrowed to Mrs May and then-junior minister Andrea Leadsom, but she pulled out before members voted, leaving Mrs May to become leader unopposed.

Who could replace Mrs May?

The list of possible replacements is long with names such as Boris Johnson, Dominic Raab, Michael Gove, Sajid Javid, Jeremy Hunt and Amber Rudd all mentioned but there is no clear frontrunner. - PA / Guardian