Theresa May resigns as Tory leader: Is she still PM and who will replace her?
MPs are selecting a shortlist of two contenders, from which Tory members will choose the new leader
She will carry on governing the country and fulfilling her official duties until a successor is chosen.
The Conservative leadership contest will begin formally the week after she steps down – on 10 June.
Conservative Party rules allow a large degree of flexibility about how the leadership contest should work, stating only that Conservative MPs must whittle down the number of candidates to a shortlist of two to be presented to members in the country for a final choice.
The exact means of doing this is decided afresh by the executive of the backbench 1922 Committee, in consultation with the party board, each time a contest takes place.
With concern mounting that the crowded field – which at one point reached 13 contenders – would mean a long and unwieldy election period, Committee officials last week announced a new format designed to cull no-hopers early in the process.
Candidates now require the nominations of eight other MPs to stand, rather than the proposer and seconder demanded in previous contests.
In a first ballot of Conservative MPs on 13 June, candidates with fewer than 17 votes will be eliminated. If all receive 17 or more votes, the least popular goes out. If there is a tie for last place, officials will speak to the two candidates involved to see whether both should drop out or the ballot be re-run.
A second ballot will be held on 18 June, with candidates needing 33 votes or more to survive. Again, if all pass the threshold, the one at the bottom of the list will be removed.
By this point, the field should have been considerably narrowed, and further rounds of voting will take place on the following days in the hope of producing a final two by Thursday 20 June
Between each ballot, intensive horse-trading can be expected in Westminster as the surviving candidates seek to poach one another’s supporters and hoover up the backers of eliminated candidates.
The final two contenders will go through to a postal ballot of an estimated 160,000 party members around the country in July, with the result currently expected in the week of 22 July.
It emerged on Thursday that there is no guarantee the new leader’s name will be announced before parliament breaks up for its summer recess, potentially denying the opposition an opportunity to test whether he or she can command a majority in the House of Commons as prime minister.