LONDON, United Kingdom (AFP) — Rishi Sunak is set to be installed today (UK time) 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 members of parliament, and Boris Johnson dramatically aborted a comeback bid.

The 42-year-old Hindu will be Britain's first prime minister of color 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 6 September 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 a.m., 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."

After delivering the now all-too-familiar new leader's speech from the steps of Number 10 at around 11:35 a.m., 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 stabilizing 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".