Unlike his mother Queen Elizabeth II, from a very young age King Charles III knew exactly what would be expected of him when the time came. Compared to the then Princess Elizabeth's younger years, there was no expectation she would ever be head of state.
It was only down to a twist of fate in 1936 when the princess's uncle, King Edward VIII, voluntarily abdicated the throne that changed the line of succession. Her father, George VI, was proclaimed king before she took over the Crown just 15 years later. In contrast, the late Queen had been able to prepare her children and grandchildren over the course of her 76-year reign for their inevitable duty.
Here, we take a look at how Her Majesty, who died last Thursday at Balmoral, paved the way for the country's new King Charles and future king Prince William, who is next in line to the throne, and his eldest Prince George:
Practice audiences
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The Queen allowed Charles to hold practice audiences with David Cameron to prepare for him taking over.
The former Conservative Prime Minister said the new monarch had served the "longest apprenticeship in history" and he believed he would be "brilliant" in the role.
The Prime Minister of the day holds a private weekly audience with the monarch to discuss matters of government.
The meetings, held at the Audience Room in Buckingham Palace, are a key part of the PM's diary and provided the 15 leaders who served during the Queen's reign with an opportunity to seek her counsel.
Mr Cameron disclosed that he had held practice sessions with the-then Prince of Wales when he was still in office.
"I had audiences with Prince Charles when Queen Elizabeth II was on the throne because he wanted to start thinking about how to conduct those audiences," Mr Cameron told the BBC's Sunday With Laura Kuenssberg.
"I saw him in action at Commonwealth heads of government meetings and he knows everybody personally, he interacts with them brilliantly," Mr Cameron added.
State papers
According to one royal expert, the Queen had asked Charles to start looking at confidential state papers so he was prepared to quickly take over, Daily Star reports.
Robert Jobson, author of the 2002 book Diana, last year said the death of the Duke of Edinburgh aged 99 marked a 'sea-change' in the Prince of Wales' position within the royal family.
Writing in the Evening Standard, he described the new procedure as part of the latest in a "series of handovers", which included sending the then Duke and Duchess of Cambridge on an official engagement to the Caribbean.
Describing the discussions around Charles' new responsibilities, he wrote: "The Queen, known as Reader Number One in Whitehall, wants Charles to be kept up to speed with all confidential state matters so that the transition is as smooth as possible should anything happen to her."
He added that the Prince would be the "most well-prepared monarch-in-waiting ever" as he has already been involved in meetings with the government for several decades, such as proposals for new legislation and notes from the Cabinet Office.
Cover at engagements
In later years, as the Queen's health deteriorated, King Charles and Prince William stepped in for Her Majesty on official engagements as part of their training.
Earlier this year in May, due to ongoing mobility issues, the Queen gave the authority to Prince Charles and Prince William, as counsellors of state, to open Parliament on her behalf.
For the first time, King Charles read the opening speech to mark the formal start of the parliamentary year.
He had covered for the Queen on other recent occasions too, such as the laying of wreaths at the Cenotaph last Remembrance Day - which the Queen had to pull out of.
And also in the days just before her death. On Saturday, September 3, the Queen missed the Braemar Gathering - the popular Highland Games event that she usually attends every year.
It is understood the decision was taken for the comfort of the head of state and King Charles attended in her absence.
Afternoon tea
The Queen and her grandson Prince William had a strong relationship that was forged from their mentoring sessions when he was a child at Eton.
They attended weekly afternoon teas and lunches, where she provided training and advice to the heir, according to OK!
"The Queen plays a very special dual role in William's life," said Katie Nicholl, author of Kate: The Future Queen, in 2021.
"She is his sovereign, but also a very loving grandmother who wants to prepare him for the future."
William had struggled with his royal birthright as a teenager which was a cause of concern for the Queen.
She began inviting him to lunch or tea with her and the Duke of Edinburgh each Sunday.
"Afterwards, he would have one-on-one time with his grandmother to talk about whatever was on his mind," the expert added.
"She was there for him to unload on – but those sessions were also an opportunity for her to mentor and teach him, as her grandfather, George V, did with her.
"They became incredibly close and as his respect for her grew he began to embrace his destiny."
Prince George
At just nine years old, Prince George is second in line to the throne as Prince William's eldest child.
At the tender age of seven, he learned about the importance of his inherited role, according to royal historian Robert Lacey's book, Battle of Brothers.
"William has not revealed to the world how and when he broke the big news to his son," Lacey wrote.
"But sometime around the boy's seventh birthday in the summer of 2020, it is thought that his parents went into more detail about what the little prince's life of future royal 'service and duty' would particularly involve."
Since then, parents Kate and William have started to encourage the youngster to take part in selfless acts and causes, such as during the coronavirus pandemic when George delivered meals to their at-risk neighbours and litter-picking at his school.
They've also been making an effort to get the little boy accustomed to public appearances and large crowds, and was present at Jubilee celebrations and more recently, the Women's Euro 2022 final at Wembley.
You can now buy Friday's historic Daily Mirror commemorating the death of the Queen here: mirror.co.uk/commemorative
