What would happen if Theresa May resigned?

The Prime Minister seems set to win the votes in the House of Commons on the Queen’s Speech today and tomorrow, but supposing she decided that she had secured the Government’s immediate future and it was up to someone else to get it out of the mess?

David Davis is likely to replace Theresa May should she resign (Getty)

The Conservative deal with the Democratic Unionist Party means that Theresa May has a majority in the House of Commons for its critical votes on the Queen’s Speech. Today MPs will vote on Labour’s alternative programme for government. Unless the DUP has a last-minute change of heart, it will be defeated. And then tomorrow MPs will vote to endorse the Government’s watered-down, DUP-approved programme.

The immediate threat to Theresa May’s position has receded, but the question keeps coming up: what would happen if, having secured the Government’s future, she just quit?

What if she just said, “I’m off for a walk in the Welsh hills; someone else can get us out of this mess after all.”

The usual procedure is well known. The Prime Minister would announce her intention to stand down as soon as a successor is elected to replace her. That is what David Cameron did the day after the referendum a year ago.

We are familiar, too, with the rules for an involuntary departure. Fifteen per cent of Conservative MPs, currently 48, would have to write to Graham Brady, chairman of the 1922 Committee, which represents Tory backbenchers, to ask for a vote of no confidence in the leader. If that vote among all Tory MPs is carried, an election is then held, in which the leader may not stand. The device has been used in opposition, against Iain Duncan Smith in 2003, but not while the party has been in government. Even so, the rules are well known, and they assume that the Prime Minister would continue in office until a successor has been elected.

But what would happen if she resigned now, or this weekend, with immediate effect?

It may not be likely, but it is an interesting question. It is similar to that which has troubled the most senior civil servants (and constitutional historians such as Lord Norton) from time to time: What if the Prime Minister dies?

There are no fixed rules. Robin Butler, the former Cabinet Secretary, told the House of Lords a while ago: “I think that this question is too difficult and that it would have to be solved pragmatically in the circumstances in which it arose.”

He explained he had thought about it: “I remember being concerned about this after the Brighton bomb. If the Prime Minister were assassinated, what would happen in the interim? I tried to suggest some procedures but at that point the cabinet was not really inclined to take them seriously.”

A prime minister hasn’t died in office since Lord Palmerston in 1865. He was succeeded, in the days when leaders would “emerge” from private conclaves of great men, by Lord Russell, his Foreign Secretary, who had been Prime Minister before.

However, Lord Butler explained what he thought would have happened if Margaret Thatcher had been killed in 1984: “I am quite sure that the cabinet would have had a discussion and the Queen would have sent for a member of the cabinet – someone whom the cabinet had agreed on – to hold the position in the interim while the election procedures were gone through.”

Curiously, the Labour Party wrote into its rules what would happen under a Labour government. Prompted by the death of John Smith as leader of the opposition in 1994, chapter 4, clause II, 2, E, i now reads: “When the party is in government and the party leader is prime minister and the party leader, for whatever reason, becomes permanently unavailable, the cabinet shall, in consultation with the NEC, appoint one of its members to serve as party leader until a ballot under these rules can be carried out.”

It would seem that there is a consensus, then. If Theresa May should become, in the delicate words of the Labour Rule Book, “permanently unavailable”, the Cabinet would meet and agree to recommend to the Queen that she invite one of their number to form a government. That Cabinet meeting would be chaired by Damian Green who, as First Secretary of State, would be the highest-ranking minister in the Prime Minister’s absence.

Just as the Labour rules specify that the Cabinet would consult the party’s National Executive Committee, no doubt Green would consult Brady, as chairman of the 1922 Committee, which represents backbench Conservative MPs, and Rob Semple, the chairman of the Conservative Party Board, representing the party in the country. But the decision would be taken by the 22 full members of the Cabinet.

Despite some of the hopes of Labour supporters, there is no prospect that Jeremy Corbyn would become prime minister as long as the DUP agreement holds.

The constitutional theory is that the leader of the Conservatives, with the support of the DUP, could expect to command a majority in the House of Commons and so is the person who should be invited by the Queen to form a government. It is a question for the Conservative Party who its interim leader would be, pending the election of a permanent replacement. And the Cabinet is the highest body that happens to combine the parliamentary Conservative Party and the Government.

So who would they choose? I think that would depend on how and why May had become “permanently unavailable”, and what had happened in the days and hours before the Cabinet met. But the obvious candidates would be Boris Johnson, David Davis, Amber Rudd and Philip Hammond. At the moment Johnson doesn’t seem likely, while Rudd and Hammond might be considered too strong Remainers. Whoever is chosen would have a big advantage in the leadership election, because they would be fighting it as a new prime minister. There is no precedent for a temporary prime minister in the British constitution. The Cabinet would, therefore, probably be deciding who would lead the Conservatives into the next general election.

At the moment, my best guess is that it would be the working-class boy brought up on a council estate by his single mother, ex-SAS soldier David Davis.