The former chancellor will then make his first prime ministerial address on the steps of 10 Downing Street
London: Rishi Sunak will take charge as Britain's first Indian-origin Prime Minister after an audience with King Charles III on Tuesday, a day after he was elected the new leader of the Conservative Party in a historic leadership run.
Outgoing Prime Minister Liz Truss will chair her final Cabinet meeting at 10 Downing Street on Tuesday morning before she makes her way to Buckingham Palace to formally tender her resignation to the 73-year-old monarch.
Sunak, 42, will then arrive at the palace for his meeting with the King, who will formally anoint him as the UK's new Prime Minister.
The former chancellor will then make his first prime ministerial address on the steps of 10 Downing Street, expected to be joined by wife Akshata Murty and daughters Krishna and Anoushka.
"The UK is a great country, but there is no doubt we face a profound economic challenge," said Sunak in his first address as Prime Minister-elect on Monday.
"We now need stability and unity and I will make it my utmost priority to bring our party and our country together; because that is the only way we will overcome the challenges we face and build a better, more prosperous future for our children and our grandchildren," he said.
"I pledge that I will serve you with integrity and humility and I will work day in and day out to deliver for the British people," Sunak said.
Sunak, who describes himself as a proud Hindu, is the UK's first Prime Minister of South Asian heritage and the youngest for more than 200 years at the age of 42. His victory on Diwali has resonated among the Indian diaspora groups across the UK, who have hailed it as a historic moment in British social history.
Rishi Sunak becoming the first British Indian Prime Minister is a historic moment. This simply would not have been possible even a decade or two ago, said Sunder Katwala, Director of the British Future think tank.
But we should not underestimate this important social change. When Sunak was born in Southampton in 1980, there had been no Asian or black MPs at all in the post-war era. There were still no black or Asian Conservative MPs when he graduated from university in 2001. That Rishi Sunak is set to be Prime Minister during the coronation of King Charles III next spring tells an important story about our society, where we have come from and where we are going in the future, he said.
The Archbishop of Canterbury urged Britons to pray for Sunak as he enters No. 10 Downing Street at a turbulent time.
"At a time of great difficulty and uncertainty for this country, please join me in praying for Rishi Sunak as he takes on the responsibilities of leadership," Justin Welby wrote on Twitter.
"May he, and all leaders of all parties, work across divides to bring unity and offer stability for those who need it most," he said.
Sunak's victory in the Tory leadership race came at the end of a dramatic few days in Westminster since Truss resigned last Thursday in the wake of a disastrous tax-cutting mini-budget and several policy U-turns. Former prime minister Boris Johnson ruling himself out from the contest over the weekend and Leader of the Commons Penny Mordaunt conceding defeat just moments before the shortlisting deadline on Monday paved the way for a remarkable political comeback for Sunak having lost the Tory membership vote to Truss just last month.
However, his popularity as the frontrunner among his party colleagues has been replicated yet again as more than half the Tory MPs came out publicly in his support. He now faces the enormous challenge of steering the UK economy through massive inflationary turbulence and also uniting the different wings of a divided Conservative Party.