Boris Johnson has resigned: When will new prime minister be in place?

The prime minister’s notice of departure has triggered a Tory leadership contest

The prime minister stepped down on Thursday (PA Wire)

Boris Johnson announced his resignation on Thursday after over 50 Tory MPs walked out from the government over his conduct.

He gave a resignation statement from a lectern outside Downing Street - as is tradition - vowing to stay on in power until a new leader is elected, most likely by October.

His resignation avoided the need for another no-confidence vote in his leadership, which was expected to take place next week once Tory MPs on the 1922 committee had changed the rules to allow it.

But it has triggered a leadership race in the Conservative party that is likely to consume politics for the next few weeks or months.

There is no obvious and clear successor to Mr Johnson, though there are a number of candidates in the running, including Liz Truss, Suella Braverman and Steve Baker who all said on Thursday they were considering it.

Other names mentioned include Rishi Sunak, who was previously seen in Westminster as the obvious successor but whose stock has fallen in recent months.

Others include Penny Mordaunt, a favourite among Tory members, and Ben Wallace the defence secretary.

Yet more runners and riders also include Jeremy Hunt, Sajid Javid, Nadhim Zahawi, and Tom Tugendhat – it really is a wide-open field.

The timescale of the leadership contest will be decided by the Conservative party's 1922 committee and is not clear yet. Crucially, Mr Johnson has indicated that he wants to stay as caretaker prime minister during the process.

All the MPs who want to take part will face a vote of Tory MPs, with the least popular candidate eliminated.

Successive rounds of votes will then take place among Tory MPs – and crucially, the transfer of their supporters to other candidates – will whittle down the field to a final two candidates.

Those final two candidates will then be put to the Tory membership, which will make the final decision.

Boris Johnson has already said he will stay in office as caretaker until this process is completed. Then he would go to the palace and resign in a short audience with the Queen, and another MP would also go to the palace and ask to form a government. After that, the victor would head straight to Downing Street, and likely address the public from the doorstep.

Though there may be some resistance to Mr Johnson remaining in office due to the manner of his departure.

If that comes to a head within the Tory party then we may see a no-confidence vote after all – either in parliament or within the Tory party. This will become clear in the coming days.

At no point in this process will there be an election or public vote to choose the new prime minister – though they might choose to call an early election to get their own mandate.