Rishi Sunak will on Tuesday be installed as Britain's third prime minister this year, replacing the humiliated Liz Truss after just seven weeks and inheriting a daunting array of problems.
Sunak became the ruling Conservatives' new leader on Monday after rival contender Penny Mordaunt failed to secure enough nominations from Tory MPs, and Boris Johnson dramatically aborted a comeback bid.
The 42-year-old Hindu will be Britain's first prime minister of colour and the youngest in more than two centuries.
Sunak will take power in a morning audience with King Charles III, who is anointing his first prime minister since ascending the throne just two days after his late mother Queen Elizabeth II appointed Truss.
The ceremony on September 6 was the last major public act of her record-breaking reign.
Truss will hold a final cabinet meeting before making a departing statement in Downing Street at around 10:15 am (0915 GMT), with Sunak expected to speak just over an hour later.
She leaves office as the shortest-serving premier in history, after a calamitous tax-slashing budget sparked economic and political turmoil.
The 47-year-old announced her resignation last Thursday, admitting she could not deliver her "mandate" from Conservative members -- who had chosen her over Sunak in the summer.
He has now staged a stunning turnaround in political fortunes, and vows to do the same for Britain as it confronts decades-high inflation, surging borrowing costs and imminent recession.
Addressing the public on Monday, Sunak promised "stability and unity" as well as bringing "our party and our country together".
‘Choices'
After delivering the now all-too-familiar new leader's speech from the steps of Number 10 at around 11:35 am, Britain's fifth prime minister in six years will start appointing his top team before facing his first session of "Prime Minister's Questions" in parliament on Wednesday.
Finance minister Jeremy Hunt, appointed by Truss just 11 days ago in an ultimately futile bid to salvage her premiership, could remain in the role after stabilising the markets.
He endorsed Sunak on Sunday, writing in the Telegraph that he was a leader "willing to make the choices necessary for our long-term prosperity".
After reversing almost all of Truss's various tax cuts, Hunt has warned "difficult decisions" loom over public spending.
Whoever heads the Treasury is set to unveil the government's much-anticipated medium-term fiscal plans on October 31, Halloween, alongside independent assessments.
Sunak must also decide whether to appoint to his cabinet senior MPs who did not support him, such as Mordaunt, in a bid to unify his fractured party.
One so-called big beast unlikely to get a seat around the table is his former boss Johnson, who was driven out in July partly thanks to Sunak's resignation.
The pair met late Saturday, when Johnson reportedly urged him to form a power-sharing partnership.
The ex-leader had only secured the public backing of a few dozen Tory MPs, compared to well over 100 for Sunak, and the offer was rebuffed.
A day later, Johnson bowed to political reality and announced he would not move forward with his audacious comeback.
"You can't govern effectively unless you have a united party in parliament," he acknowledged.
'No mandate'
Sunak, a wealthy descendant of immigrants from India and East Africa, is also facing calls for a general election after becoming the latest UK leader who lacks a direct mandate from the electorate.
Pollster Ipsos said Monday that 62 percent of voters want a vote by the end of the year.
"He has no mandate, no answers and no ideas," Labour's deputy leader Angela Rayner tweeted.
Scottish leader Nicola Sturgeon, whose nationalist government wants to hold an independence referendum next year, echoed the comments -- while recognising the significance of Britain getting its first leader of colour.
The next election is not due until January 2025 at the latest and opposition parties have no way to force one, unless dozens of Conservative MPs acquiesce.
That appears unlikely as a flurry of polls show Labour with its largest lead in decades.
YouGov modelling Monday showed Sunak faces an uphill battle to restore confidence in both the Tories and himself.
Weekend responses from 12,000 people found that Labour leader Keir Starmer was seen as the "best prime minister" in 389 constituencies, compared with Sunak's 127.
