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15 and counting: The Queen prepares to appoint her newest PM

London(CNN) We're back, royal readers, and just in time, with the announcement Monday of Liz Truss as the new leader of the governing Conservative Party -- and consequently, the country's next prime minister. As you'll recall, the Queen and politics don't usually mix, but she is involved in the transition, so let's break it down.

As head of state, the appointment of new prime ministers is one of Elizabeth II's core constitutional duties, along with the State Opening of Parliament and signing parliamentary bills into law. Truss will be the Queen's 15th prime minister when she takes over from Boris Johnson on Tuesday.

Normally, the practicalities are straightforward. In a nutshell, the outgoing PM makes a statement outside 10 Downing Street and then heads off to Buckingham Palace for a final farewell audience with the monarch. Shortly after, their successor travels over for their appointment. All in all, it's relatively quick, taking around half an hour. However, this time ... not so much.

The sovereign had intended to interrupt her vacation in Scotland and return to London to appoint the new PM. But in a break with royal tradition, Buckingham Palace announced Wednesday that the 96-year-old will not be making the 1,000-mile round trip, with the outgoing leader and his successor traveling to Balmoral on Tuesday instead.

According to a royal source, the decision to hold the two audiences at her Scottish country residence rather than at Buckingham Palace -- for the first time in her 70-year reign -- was made to provide certainty to the Prime Minister's diary. The source told CNN the decision was to avoid any last-minute alternative arrangements in the event the Queen finds herself experiencing any episodic mobility issues. As a result, Tuesday will likely be a more protracted event due to the distance between London and Balmoral and the logistics involved.

The decision also makes sense, given that more recently the Queen's presence has generally been confirmed on the day depending on how she is feeling. Case in point, a royal source told CNN Friday that the Queen would miss the annual Braemar Gathering this weekend but that Prince Charles, who usually accompanies her, would still be at the Highland Games. The decision was made for the Queen's comfort, the source said.

File photograph of Balmoral Castle.

The protocols for prime ministerial appointments are unwritten -- based instead on constitutional convention, according to experts.

"It's all a matter of convention that we just have a prime minister -- one minister who is more important than the others -- and that means that there are no real legal formalities to undergo for the appointment," explained Craig Prescott, a lecturer in law at Bangor University in Wales.

"Historically, the monarch would have had a much greater flexibility over who that primary adviser would be," he told CNN. "That discretion has ebbed away because there are now constitutional conventions in place that regulate who the prime minister is.

"It's very much for the political parties, and for the electorate, to ultimately decide who the prime minister is -- and the Queen effectively puts that decision into action," he added.

Prescott said the Queen is still involved because "it has to be remembered that the government is still carried on in the name of the crown. It is still 'Her Majesty's Government.'"

So how will Tuesday unfold? Well, at some point, Johnson will arrive and tender his resignation as prime minister and First Lord of the Treasury. (Fun fact: Most assume 10 Downing Street is the official residence of the prime minister but it's in fact that of the First Lord of the Treasury, a role usually held by the PM.) One of the last acts of the office is to advise the monarch on their successor (even if it's already been decided through a leadership contest). This is yet another quirk of proceedings, but one that ensures the Queen remains politically neutral, according to Prescott.

The Queen chats with Boris Johnson during a reception at Windsor Castle last October.

Little is truly known about these occasions, but some of Johnson's predecessors have touched on them in their memoirs. Gordon Brown said the final official duty of going to see the sovereign doesn't involve handing over seals of office or anything, but rather "simply saying goodbye to the Queen -- and thanking her."

In his autobiography, "My Life, Our Times," the former Labour prime minister said that "as usual, she was charming and the occasion itself was relaxed." Brown also recalled how the Queen humanized the situation by permitting his two young sons to be present when he received a parting gift -- an inscribed photograph of the monarch.

"Fraser was just four, and when he looked at the photo he said, 'That's the Queen!' -- as if it was of someone other than the person who had just handed it to him. Queen Elizabeth, startled by his response, replied: 'But I'm the Queen, I'm the Queen.' We laughed, and then we left," Brown wrote.

A short while later, the Queen will call up Johnson's replacement for a ceremonial audience known as "kissing hands." Whether or not actual hands are kissed is up for debate. Some past PMs, like David Cameron, have said the name isn't literal, while others have suggested it is.

Former prime minister Tony Blair described understanding "kissing hands" as "the laying on of the Queen's authority to govern." However, when it came to the moment, he wasn't exactly sure what that meant. In his autobiography, "A Journey," the former Labour leader recalls waiting in an antechamber to be presented to the Queen, before becoming abruptly anxious.

"A tall official with a stick stood by me. 'I should tell you one thing, Mr Blair,' he began (note 'Mrk Blair' until I had been appointed), 'you don't actually kiss the Queen's hands in the ceremony of kissing hands. You brush them gently with your lips,'" Blair wrote.

Tony Blair greets Labour supporters outside 10 Downing Street after a historic landslide election in May 1997.

Blair said he was "floored" by the remark but was left with little time to mull it over. "While I was still temporarily disconcerted, the door opened and I was ushered in, unfortunately tripping a little on a piece of carpet so that I practically fell upon the Queen's hands, not so much brushing as enveloping them," he continued, adding that the rest of the occasion went off without a hitch.

Meanwhile, the changing of location matters little constitutionally, with Prescott recalling how Herbert Henry Asquith traveled to meet King Edward VII, who was in the French city of Biarritz, to take office. It is the only appointment to have ever occurred on foreign soil and "reflects how there are so few formalities about this."

Instead, the fact that the Queen has allowed the process to be adapted for her will likely be what's important to Johnson and Truss.

"I think both the outgoing prime minister and the incoming prime minister will very much want that moment with the Queen. They will want to be seen to have a historical continuity with what's gone before. I think that that will be very important for them," Prescott said.

And amending the ceremonial formalities will also go some way to alleviating concerns from royal-watchers over her health. The fact that the monarch is making the concession to host the audiences at Balmoral rather than issue a directive authorizing Charles and his eldest son, Prince William, to step in -- as they did to open Parliament in May -- gives yet another indication that neither age nor mobility difficulties will stop the resolute sovereign from carrying out her royal duties.

FEATURED PHOTOS

The Queen has been served by 14 prime ministers during her reign so far. Many relationships were formed, from Winston Churchill to "Iron Lady" Margaret Thatcher -- with some proving more difficult than others.

In celebration of the Queen's Diamond Jubilee, which marked 60 years as British sovereign, then-prime minister David Cameron hosted a lunch at Downing Street for the monarch. The occasion was also an opportunity to catch up with several of her former premiers. Here she stands with Cameron (left), John Major (2nd from left), Tony Blair (2nd from right) and Gordon Brown (right) on July 24, 2012 in London.

Winston Churchill (1951-1955): The Queen was said to be in awe of her first prime minister, Winston Churchill. Once when asked which PM she enjoyed meeting with most, she replied: "Winston of course, because it's always such fun."

Harold Wilson (1964-1970, 1974-1976): Wilson, who came from a lower-middle-class background, became the Queen's first Labour Party prime minister. Wilson, seen here on the right, next to Prince Philip, often broke away from protocol, and he enjoyed helping with the washing-up after barbecues at Balmoral -- one of the Queen's residences. The Queen, however, warmed to Wilson's informal presence and even invited him to stay for drinks after their first meeting, which was not commonplace.

Margaret Thatcher (1979-1990): While Thatcher and the Queen were the closest in age, Thatcher kept their encounters strictly professional, formal and famously stiff. The "Iron Lady," as she became known, reportedly had a tense relationship with the monarch during their traditional weekly meetings. Thatcher also viewed her annual visits to the royal home in Balmoral as interrupting her work. Despite this, Thatcher is said to have been incredibly respectful of the Queen and eventually became her longest-serving prime minister.

Check out more photos from the archives in our gallery looking at the Queen and her prime ministers.

NO UK PM HAS EVER RAISED CONSTITUTIONAL QUESTIONS THE WAY JOHNSON HAS

Analysis from CNN's Luke McGee, UK and European Policy and Politics Editor

The Queen will finally see the back of Boris Johnson -- for now at least. The prime minister will officially resign to the monarch on Tuesday.

While Her Majesty never makes her political opinions known and defers to her advisers and government ministers on almost all matters, you'd forgive Elizabeth II for breathing a sigh of relief.

Johnson has on more than one occasion pushed the monarch's position of impartiality to its limits and led to Brits asking questions that once seemed unfathomable.

Early on in his premiership, Johnson prorogued -- or suspended -- Parliament, so that lawmakers would not be able to intervene and stop the Brexit deadline from expiring, forcing Britain to crash out of the European Union with no deal. The Queen followed her prime minister's advice allowing the prorogation -- only to later be told that the advice Johnson had given her was unlawful. Many called for Johnson to apologize for embarrassing the monarch.

And it wouldn't be the only time in his premiership that his government would have to do so. Officials were left with little other choice in January when revelations about pandemic lockdown-busting parties emerged out of 10 Downing Street, including one on the night before Prince Philip's funeral.

Boris Johnson's first audience with the Queen as prime minister on July 24, 2019.

As Johnson's position became untenable earlier this year, there were fears that his refusal to resign, despite mass protest from his own cabinet, would once again force the Queen and her advisers to act.

Had Johnson clung to power, he could have found himself removed as Conservative leader and without a government serving him. Due to the UK's odd un-codified constitution, he could have remained prime minister of around 66 million people, creating a host of new problems to resolve. Fortunately, it didn't come to that and Johnson has decided to make a (relatively for him) quiet exit.

Johnson is a man who has always described himself as a monarchist who holds the Queen in the highest regard. And critics might say he could have demonstrated this respect by not bringing the country's constitution to breaking point and dragging her into the mucky business of politics.

WHAT ELSE IS HAPPENING?

BBC donates to charities linked to Diana.

Britain's public service broadcaster has given £1.42 million ($1.64 million) to seven charities connected to the late Princess Diana. The amount reflects the sales made from the 1995 Panorama interview with the Princess of Wales, which an independent inquiry last year determined was secured using "deceitful" methods. The charitable donations come from the BBC's commercial revenue rather than the taxpayer's license fee, the broadcaster said. "The BBC had indicated its intention to donate to charity the sales proceeds derived from the 1995 Panorama interview with Diana, Princess of Wales. The BBC has now done so. Given the findings of Lord Dyson, we think this is the right and appropriate course of action," the organization said in a statement Friday.

Harry and Meghan are back.

We're pretty sure you won't have forgotten, but just a reminder that the Duke and Duchess of Sussex will be visiting the United Kingdom and Germany this week. A spokesperson for the Sussexes told CNN that the pair "are delighted to visit with several charities close to their hearts in early September." The couple are due to attend the One Young World 2022 Manchester Summit on Monday, then head to the Invictus Games Düsseldorf 2023 One Year to Go event in Germany on Tuesday, before flying back to the UK for the WellChild Awards 2022 in London on Thursday. Meghan has been making headlines in recent weeks after her much-anticipated podcast "Archetypes" dropped on Spotify. The first two episodes featured G.O.A.T. Serena Williams (discussing the gendered connotations of "ambition") and superstar singer-songwriter Mariah Carey (talking biracial identity).

The Sussexes at the 2020 Invictus Games in the Netherlands.

Prince Charles edits special edition of Black British newspaper.

The Prince of Wales has guest-edited a special issue of British African-Caribbean newspaper The Voice to mark its 40-year anniversary. Founded in 1982, the paper is the only national Black newspaper operating in the UK. Prince Charles described the publication as "crucial," before adding that he was "so touched" to be asked to helm the special edition. Clarence House said Charles' issue "touches on themes including community cohesion, education, climate, the Commonwealth, faith and the arts." It was released on Thursday and features interviews with actor Idris Elba and Doreen Lawrence, the mother of 18-year-old student Stephen Lawrence who was murdered in an unprovoked racist attack in southeast London in 1993, among others. Read more here.

Prince Charles visits the 2nd Battalion of The Mercian Regiment before it is amalgamated with The 1st Battalion, at Weeton Barracks, on July 8, 2022 in Weeton, Lancashire, England.

PHOTO OF THE WEEK

Messages and photographs of Diana, Princess of Wales are seen on the gate of Kensington Palace Wednesday as fans gather outside her former London home on the 25th anniversary of her death.

See more photos of Diana and her impact in our gallery.

REMEMBERING DIANA

Diana, Princess of Wales leaves Chelsea Harbour Club, London in November 1995.

Twenty-five years after her death, Princess Diana remains a style icon -- now with a younger wave of fashion lovers finding joy in her everyday looks. CNN Style's Megan C. Hills explores her enduring legacy, from TikTokers painstakingly recreating her workout outfits to fashion fans sourcing cult items worn by the late royal. Read the full story here.

FROM THE ROYAL VAULT

Over the course of her reign, the Queen has tried to set the standard for her family. One aspect she has staunchly stuck to is to remain above politics. In this 2019 video from the CNN archive, Max breaks down exactly why she doesn't share her political views and what it could mean if she did.

At least 33 million people have been affected by deadly flooding in Pakistan, the country's climate change minister said on Thursday. Officials have called on international partners to provide aid given Pakistan's "limited" resources. Following this call to action, Prince Charles revealed he had donated to global aid charity Islamic Relief. The Prince of Wales said he and his wife were "deeply saddened" by the humanitarian disaster and paid tribute to the government and emergency responders for their relief efforts. "Times like these remind us of the fragility of our planet and the urgent need for humanity to live in harmony with Nature. Our prayers are with all our friends in Pakistan," he added.

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