In her last hours as prime minister, Mrs May arrives at the Palace of Westminster for Prime Minister's Questions.

Afterwards, she'll make a speech outside No 10 before visiting the Queen to tender her resignation.

Image source, Getty Images

So who is Boris Johnson's new senior adviser and what has he worked on in the past?

Back in 2004, Dominic Cummings helped run the referendum campaign against setting up an elected regional assembly in the North East - a vote his side emphatically won with 78% voting against it.

Between 2007-2014, he worked as Michael Gove's adviser - during which time Mr Gove served as Education Secretary in the coalition government.

In 2015, he was appointed campaign director of Vote Leave - an organisation set up to campaign for Leave in the EU referendum. He's credited with creating its "take back control" message and the controversial slogan about spending £350m-a-week extra on the NHS.

Since the referendum, he has often been outspoken on the Brexit process.

In 2018 he said the government had "irretrievably botched" the Brexit process. He said Brexit was destined to be a "train wreck" and said Tory MPs should get rid of Theresa May.

He has also previously described some Brexiteer MPs as a "narcissist-delusional subset" of the European Research Group (ERG).

In March 2019 he was found to have committed contempt of Parliament by not appearing to give oral evidence when ordered to in 2018.

Mr Cummings said he had offered to give evidence under oath but had been ignored.

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Brexit is what the UK wants right now, rather than politicians debating general elections, says Brexit Party MEP Ann Widdecombe.

Yesterday, Nigel Farage floated the idea of an electoral pact with the Conservatives in future general elections to unify the pro-Brexit vote.

"Nigel Farage is offering a very clear vision" for the UK, where the country is "free" of EU rules and regulations, she says.

On warnings from the IMF, Ms Widdecombe says "we've heard it all before".

A no-deal Brexit won't be plain sailing but it won't be a disaster either, she believes.

Dominic Cummings - the former chief of Vote Leave - is expected to become a senior adviser to the new prime minister.

Mrs May leaves No 10 for her last ever Prime Minister's Questions.

Media crews are gathered in front of No 10 awaiting any movement, as Theresa May prepares to hand over to successor Boris Johnson.

Mrs May is expected to leave No 10 before heading to the House of Commons, where she will take place in her last Prime Minister's Questions at 12:00 BST.

She'll then head back to Downing Street to speak, before travelling to see the Queen to resign.

Image source, EPA

Image source, EPA

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"There's been things he hasn't done as well as he could have done" says former foreign office minister Alistair Burt on Boris Johnson's record as foreign secretary.

"The person in charge has got to have sufficient grasp of the detail in order to do that job," he states.

He says that he was supportive of Jeremy Hunt as leader.

SNP MP Pete Wishart delivers his verdict on the new PM:

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Former Conservative party chairman Michael Heseltine confirms he did not vote for either Boris Johnson or Jeremy Hunt and says he will not vote for anyone who "wants to make this country poorer or less powerful".

"Wherever I go I meet Conservatives who say they could not vote for a Brexit-supporting prime minister," he says.

"I think there's a high chance we won't leave," he says, adding that a second referendum could reverse the current course, but a general election "could perpetuate" the "instability" in Parliament.

"There is no prospect of a majority" out of a general election, currently, he adds.

Image source, Getty Images

PM's come and go, but the Downing Street cat, Larry, remains in situ.

Larry currently holds the official role of chief mouser to the Cabinet Office, a position that's said to date back hundreds of years.

How have previous PMs warmed to their four-legged civil servant over the years? Find out here.

Sarah Wollaston - who left the Conservative Party in February to join a new independent group of MPs - is not impressed by Boris Johnson's new appointment.

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Going ahead with Brexit is a long term, "probably minimum decade long" endeavour, warns Conservative former education secretary Justine Greening.

It will take up years of work for government, she says, and people must have a vote on the deal that has been negotiated.

A no-deal Brexit "is the most fundamentally un-Conservative thing" she says she has ever come across, as it will increase unemployment and borrowing.

Foreign Office Minister Harriett Baldwin says "under the surface" Theresa May "did a lot of work" in defence and foreign affairs. But she speculates policing is the kind of area Mr Johnson will focus on immediately in office.

A quick history lesson from Stephen James on Twitter.

Boris is the 14th Prime Minister to hold the position during the Queen's reign, and the 10th Conservative PM:

BBC Radio 5 Live

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Brexit needs to happen so that the government can get back to focusing on domestic issues, Communities Secretary James Brokenshire says.

He says this would also give "stability and certainty" to businesses.

"The last thing we need at the moment is a general election," he says, adding that Boris Johnson will give the UK a sense of "optimism".

He is confident Mr Johnson will use the summer recess to go and talk to Brussels about Brexit.