What needs to happen for there to be a leadership contest?
A leadership challenge can be triggered if 15 percent of members of parliament in May’s Conservative Party write a letter to the chairman of the party’s so-called “1922 committee”.
The Conservatives currently have 316 members of parliament (MPs) so 48 of them would need to write such letters to challenge May.
Once that threshold has been reached, the chairman will announce the start of the contest and invite nominations.
Could this happen to May?
The chairman of the 1922 committee is the only person who will know exactly how many members of parliament have submitted letters of no confidence.
But some eurosceptic members of parliament have started submitting letters to the committee chairman in protest over her Brexit negotiating strategy.
What will happen during a no confidence vote?
If a no confidence vote is called then all serving Conservative members of parliament will be able to cast a vote for or against the serving leader.
If May wins any confidence vote she remains in office. If she loses, she is obliged to resign and barred from standing in the leadership election that follows.
As noted elsewhere, May’s loss of six cabinet ministers in eight months is unprecedented.