David Cameron will return to the cabinet table for the first time in more than seven years on Tuesday after his recall to government.
Rishi Sunak will meet his new cabinet after a dramatic overhaul on Monday saw the former prime minister return to frontline politics.
He replaces James Cleverly, who was moved to be home secretary to take over from Suella Braverman.
Mrs Braverman was sacked following her criticism of the Metropolitan Police.
Lord Cameron, as he is now known as of his appointment to the House of Lords on Monday, had been out of Parliament since he stood down as prime minister in 2016.
His return to politics came out of the blue, with Downing Street managing to prevent any rumours of the appointment from leaking, despite the fact the job offer was made last week.
In one fell swoop, No 10 revealed not only was the former prime minister entering the House of Lords, he would also be taking up one of the most senior jobs in government.
While the news was still being digested in Westminster, Lord Cameron was carrying out official duties, including holding a call with US Secretary of State Antony Blinken.
The pair "reiterated the strength and depth of the relationship between the UK and the US", the Foreign Office said, and spoke about the war in Ukraine.
In a statement, the Foreign Office said: "They discussed the conflict in the Middle East, Israel's right to self defence and the need for humanitarian pauses to allow the safe passage of aid into Gaza."
In a speech at the Lord Mayor's Banquet in London on Monday night, Mr Sunak said he was "pleased to have appointed a new foreign secretary" and said the new cabinet is "a united team".
Richard Holden, the newly-appointed Conservative Party chair, told OceanNewsUK that Lord Cameron had returned "out of a sense of duty" and would bring experience to the role.
But not everyone in the Conservative Party is pleased about the return of Lord Cameron and the new-look cabinet.
One backbencher, Dame Andrea Jenkyns, has already submitted a letter of no confidence in the prime minister. There would need to be 53 before his leadership is threatened.
And Conservative former cabinet minister Sir Jacob Rees-Mogg said the Tories were "in danger of losing votes to the Reform party".
Reform leader Richard Tice was "as happy as can be" when he saw him earlier, he told OceanNewsUK Newsnight, adding: "The champagne will be flowing in the Reform party headquarters tonight after what's been done today."
Opposition parties have been quick to ask whether bringing back a prime minister who left office seven years ago is really the fresh start Mr Sunak claims to offer.
Shadow chancellor Rachel Reeves said voters would be "wondering how David Cameron coming back into government will help them pay for their weekly shop".
She added that the Conservatives were "out of ideas" and could not offer "the change our country is crying out for".
Liberal Democrat leader Sir Ed Davey said it "sounds like desperation".
The Lib Dems are also calling for Lord Cameron's peerage to be blocked, referring to his lobbying for collapsed finance company Greensill Capital.
Lord Cameron said he had resigned from the various business and charitable roles - including president of the Alzheimer's Society - he had held since quitting as prime minister.
"I have one job - to be foreign secretary and work with the prime minister for the UK to be as secure and prosperous as possible in a difficult and dangerous world," he said.
He insisted the Greensill affair was "in the past" and had been "dealt with".
Lord Cameron is not the only familiar face returning to the government after Monday's reshuffle.
Former Business Secretary Andrea Leadsom has taken on a junior role in the Department for Health and Social Care, while Damian Hinds has become a minister in the Department for Education, which he used to run.
