We have a new Prime Minister: so what happens now?

Theresa May is due to take over as Prime Minister after her only rival for the Conservative Party leadership, Andrea Leadsom, withdrew from the race.

What happens next?

The Conservative Party’s board will formally confirm that Ms May is its new leader, and that the leadership election due to conclude on 9 September will not take place.

When will May become Prime Minister?

On Wednesday evening. David Cameron will chair his final Cabinet meeting tomorrow and answer questions at Prime Minister's Questions for the last time on Wednesday. Ms May will be installed in Number 10 by Wednesday evening. One of her first tasks will be to announce her new Cabinet.

How does David Cameron actually resign?

He has already announced his resignation, on the morning after the country voted to leave the EU in last month’s referendum. Any PM has to formally tell the Queen, but Mr Cameron did so on that morning, when he travelled to Buckingham Palace. He will now want to officially inform the Queen that Ms May has been chosen as Conservative Party leader. The Queen is in Scotland, and so the confirmation may be done by telephone or through officials. She will return to London by Wednesday, when Mr Cameron will formally tender his resignation at Buckingham Palace. The Queen will then meet May at the Palace and formally invite her to become PM.

What is the 1922 Committee?

It is composed of all 330 Conservative MPs, including ministers as well as backbenchers. But only backbenchers vote when it chooses its chairman. Its executive committee is a powerful body that represents backbench views to the party leadership, whether it is in government or opposition.

The 1922 Committee also supervises the running of party leadership elections: to challenge a vote of confidence in the leader, 15 per cent of Tory MPs (currently 50) have to write letters to the committee’s chairman, Graham Brady.

The committee gets its name from the year in which Tory MPs agreed to set up a self-help group for the party's new arrivals at the Commons.

When was the last time this happened?

Tony Blair stood down as PM in 2007, a decision he announced the previous year after coming under pressure from allies of Gordon Brown, his Chancellor, to name his departure date. In September 2006, he promised he would leave Downing Street within a year.

Mr Brown was the only candidate in Labour’s leadership election after the left-winger John McDonnell, now the shadow Chancellor, failed to win enough MP nominations to secure a place on the ballot paper. Mr Brown went ahead with Labour Party hustings meetings around the country even though he was unopposed. He entered Number 10 in June 2007.

In 1990, Margaret Thatcher was forced out as PM after losing the confidence of her Cabinet and MPs. Her successor, John Major, was chosen by Tory MPs in an election in which Michael Heseltine and Douglas Hurd also stood. At the time, Tory members did not have a vote.

Will May have a democratic mandate?

Her allies say she has a mandate from Conservative MPs after winning the support of 199 out of 330 of them in the voting rounds that choose the shortlist of two candidates due to go into a ballot of the party’s 125,000 members. That will not happen now that Andrea Leadsom, the other candidate shortlisted by MPs, has withdrawn from the race. Ms May does not have a mandate from Tory members; although she was the favourite to win the decisive ballot, we will never know whether Ms Leadsom would have pipped her at the post (as Ms Leadsom’s campaign team believed she could).

Ms May’s supporters claim she has a mandate because we live in a parliamentary democracy and she can command a Commons majority.

Although MPs who were backing Leadsom have rallied behind May in public, they will be keen to hold her to her pledge that “Brexit means Brexit” because she backed Remain in the referendum.

How likely is a new general election?

The Liberal Democrats have demanded an early election and Ms May will face criticism that she lacks a mandate from the voters (just as Gordon Brown did in 2007 after he dropped plans for a snap election).

Ms May has said she will not call an election before the one due in 2020. She knows that holding one would add to uncertainty and instability – not least on the financial markets – at a time when there is enough turmoil after the Brexit vote.

If she changed her mind, the Fixed Term Parliaments Act, stipulating an election every five years, means she would have to persuade Tory MPs to vote for an election. At present, they do not want one that could potentially put their own seats at risk. An immediate one would allow pro-EU campaigners to try to turn the election into a referendum on last month’s referendum – and give a voice to the 48 per cent who voted Remain.

There is an outside chance that Ms May might change her tune next spring, especially if Jeremy Corbyn remains Labour leader as the Tories are confident they would beat him. She might be tempted to seize the chance of extending her party's slender majority of 12. But the odds are that May will stay on as PM until 2020 without a general election.

What has Ms May said about Brexit?

She has said that “Brexit means Brexit” in an attempt to allay fears among Tory MPs who backed Leave that, as a Remain supporter, she might try to dilute the referendum result. She wants to maintain as much access as possible to the European single market for UK goods and services. But she has also accepted that the exit terms to be negotiated with the remaining 27 EU countries must include restrictions on the free movement of EU migrants who can currently come to Britain. She said that was a key message from the voters in the referendum.

The trade-off between single market access and immigration will be the fundamental question to be resolved in the negotiations.

Ms May said she intended to invoke Article 50 of the EU’s Treaty of Lisbon after the end of the 2016 calendar year. That was based on a September timetable for taking power and so could now come forward by two months. She and her Cabinet will work out their negotiating aims. She will hope that there could be informal discussions with EU leaders now that they know who the British PM will be – even though the EU has formally ruled out such soundings.

Once Article 50 is triggered, the EU is in the driving seat in the formal talks on a new deal. The UK will be on a path out of the EU and the process is supposed to be completed in two years.

How likely is a second EU referendum?

May has ruled one out, so the answer is unlikely. However, MPs and peers who want to keep the UK in the EU have not given up hope of reversing the Brexit vote.

The Government has rejected demands for an immediate second referendum, even though a petition signed by 4.1 million people has been collected.

There is no prospect of an immediate second public vote. However, there is an outside chance of a referendum on the exit terms agreed in the UK-EU negotiations over the next two years. Jeremy Hunt, the Health Secretary, has floated this idea and is supported by many Labour MPs.

There is evidence of public support: an opinion poll by ORB for The Independent found that 40 per cent of people support a referendum on the exit terms, and that the Government should seek to remain in the EU if the deal is rejected. Although 44 per cent oppose the idea, it is backed by 12 per cent of those who voted Leave last month, which suggests that some of them may be having second thoughts.

Pro-EU politicians admit privately that three conditions would probably have to be met for a second referendum to take place: the EU deal was seen as a bad one; the economy had clearly suffered since the Brexit vote and there was strong public support for another vote.

Brexit could be overturned by a general election, if the winning party proposed to do so in its manifesto.The Liberal Democrats are likely to make such a pledge if Britain has not formally left the EU by the next election. A Labour Party under a pro-EU leader might do so, but Jeremy Corbyn would not.