Mr Sunak has held calls with several world leaders after being appointed PM yesterday, including US President Joe Biden and Ukraine’s Volodymyr Zelenskyy.
The White House said Mr Biden – who had mispronounced Mr Sunak’s name during a Diwali celebration on Monday – congratulated him on his appointment.
Both leaders “reaffirmed the special relationship” between the UK and US – and “agreed on the importance of working together to support Ukraine and hold Russia accountable for its aggression”.
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Biden gets Sunak’s name wrong
And during a conversation with Mr Zelenskyy, the Ukrainian president was assured that British support for the wartorn country would be “as strong as ever” under his premiership.
In a stark contrast with his predecessor, Mr Sunak also made time to speak with Scotland’s First Minister Nicola Sturgeon, and Welsh First Minister Mark Drakeford.
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Reshuffle: How the day unfolded
A new-look cabinet
The new PM – the third this year – is set to hold a meeting of his new-look cabinet as soon as this morning.
Mr Sunak’s top team of ministers consists of allies, former Truss backers and a number of figures from the right wing of the Conservative Party.
There’s been an element of continuity with the previous administration, with James Cleverly kept on as foreign secretary and Ben Wallace as defence secretary.
The PM has also revived the careers of experienced frontbenchers including Dominic Raab and Michael Gove, who were sacked by Boris Johnson in the dying days of his government.
But it is Mr Sunak’s decision to reappoint Suella Braverman as home secretary – days after she dramatically quit the government for breaching the ministerial code – that has been the most controversial.
Labour have accused Mr Sunak of “putting party before country” – with shadow home secretary Yvette Cooper warning: “Our national security and public safety are too important for this kind of chaos.”
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How ‘profound’ are our economic woes?
Rishi Sunak’s in-tray
Over the coming days, Mr Sunak will begin the gruelling task of uniting the Conservatives and attempting to restore the UK’s economic credibility.
The pound hit a six-week high on Tuesday in a sign that the markets approve of the country’s new leader.
Jeremy Hunt, who is staying on as chancellor after being parachuted into the role by Ms Truss following the mini-budget, is currently due to give a fiscal statement on 31 October.
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‘Tories out’: Sunak heckled outside No 10
But according to The Times, Mr Sunak – himself a former chancellor – is considering postponing this statement so he has more time to “get under the bonnet” of the Treasury’s plans.
The government is currently grappling with how best to plug a £40bn black hole in the country’s finances, amid reports both men will discuss proposals to increase taxes while squeezing public spending.
A Number 10 source has told Sky News that no decisions have been taken when it comes to pushing back the fiscal statement.