Theresa May resigns: What happens next, how does Conservative leadership contest work and who is favourite to become prime minister?

Theresa May's days in Downing Street are coming to a rapid end.

The prime minister announced her resignation date on Friday, saying she will step down as leader of the Conservative Party on 7 June. She will stay on as prime minister until a new leader is elected.

The announcement came amid mounting calls from Conservatives MP for her to quit. She angered many Tories on Tuesday by making a fresh offer on Brexit in a final bid to get her deal through parliament, including compromises on a customs union and a second referendum.

Ms May met Sir Graham Brady, chair of the 1922 Committee that represents Tory MPs, on Friday morning to announce her intention to step down.

Why has she gone now?

Ms May had previously rejected all calls to step down before she had delivered Brexit.

She had vowed to resign if MPs approved her exit deal, but had not said when she will leave office if she was unable to secure approval for her plan.

With there being little prospect of the deal passing the Commons, she came under mounting pressure to set a timetable for her departure regardless of what happens in relation to Brexit.

Her latest compromise Brexit offer prompted a fresh wave of fury among Tory MPs and sped up her departure.

House of Commons leader Andrea Leadsom resigned, while other cabinet ministers including Jeremy Hunt and Sajid Javid sought private meetings with the prime minister to tell her they could not support the plan, and many MPs stepped up their calls for her to go.

What would have happened if she refused to go?

If Ms May had refused to step down, she would likely have been being forced from office either by her cabinet or by Conservative MPs.

Both had grown increasingly frustrated at her handling of Brexit and there are now very few Tory MPs who believe she should stay in office beyond the next few weeks.

Under current Conservative Party rules, a vote of no confidence in the leader cannot be held until December - a year after the last one, which Ms May won. However, the executive of the 1922 Committee had come under pressure to change this.

The executive had already a secret ballot on whether to change the rules to allow another vote of confidence in Ms May within days. These votes would have been counted on Friday if Ms May had refused to set a date for her departure when she met Sir Graham.

Ms May would have known that, if the rules were amended, the threshold to trigger a confidence vote would almost certainly have been met. And while she comfortably saw off the bid to oust her last December, it was widely believed that there would now have been a majority among Conservative MPs for her to be forced from office.

What will happen on 7 June, when she steps down?

Ms May will step down as Conservative Party leader on 7 June, but not as prime minister.

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. Nominations will close in the same week.

The length of the contest is determined by the executive of the 1922 Committee in conjunction with the Conservative Party board.

In a joint statement released shortly after Ms May's announcement, Conservative Party chairman Brandon Lewis and 1922 committee vice-chairs Charles Walker and Dame Cheryl Gillan said the process would be completed in time for a new prime minister to be in place before parliament's summer break begins in mid-July.

Ms May is likely to use the intervening period to try to pass legislation on her pet projects - and possibly some of the less contentious parts of her Brexit deal - in order to secure some form of legacy.

How does a Tory leadership contest work?

Conservative Party rules are vague about how the leadership contest should work.

All the rules state is that Conservative MPs will whittle down the number of candidates, of which there are expected to be many, to two. This will take place in a series of sequential votes, which will to take place before the end of June.

The final two candidates will go through to a ballot of all party members, which will take place, along with a series of hustings, in early July. The current bookmakers' favourite is Boris Johnson, but at least ten senior Tories are expected to throw their hat in the ring. You can read more about all of the likely candidates here.

What does it mean for Brexit?

Theresa May's deal is dead on arrival in the Commons - so much so that, despite promising she would put it before the Commons again in early June, she is now unlikely to even bother putting it to another vote.

Even many Tory MPs who voted for it last time around, when it was defeated by 58 votes, say they will not do so again.

What this means for Britain's departure from the EU depends on who takes over as prime minister.

If, as many expect, the next leader is a Brexiteer such as Boris Johnson or Dominic Raab, they will have to decide whether to try to renegotiate the deal or leave without a deal on 31 October.

The candidates have been coy about their intentions so far and the fate of Brexit will likely become clear only during the leadership contest. All that is now certain is that Theresa May will not be the prime minister when Britain leaves the EU - if indeed it leaves at all.