His Coronation is set to be one of the biggest days of his life - and King Charles will have some of his most trusted relatives at his side.
Among them will be his beloved loyal sister Princess Anne, whose unwavering dedication to duty has seen her handed a starring role in the historic spectacle.
The Princess Royal will feature in the procession as the prestigious “Gold-Stick-in-Waiting”, a position historically handed to a person entrusted with the personal safety of the sovereign.
As a "personal aide-de-camp" to His Majesty, Anne will travel on horseback behind the new King and Queen after they are crowned at Westminster Abbey in just over a week's time.
The brother and sister duo appear to be a tight duo, with Anne being someone the King implicitly trusts - but their bond hasn't always been so strong...
Sibling rivalry and jealousy
Charles and Anne are the older two children of the late Queen and Prince Philip, with the now King just 21 months older than his sister.
Both were born before their mother became monarch and became close as they lived together at Buckingham Palace while their parents were mainly away touring the Commonwealth.
But like all siblings, they were said to have warring ways as children, with a close family friend claiming Anne would "take command of things".
Eileen Parker told royal author Ingrid Seward in her book Royal Children: "If she saw a toy she wanted, she would grab it. She also grabbed everything that Charles wanted."
Meanwhile, it has also been claimed Charles was also jealous of his younger sister's tight bond with their father Philip, with whom she shared several similar attributes.
Ingrid added in her book: "She is very much her father’s daughter—in a way that Charles could never be his father’s son."
Failed marriages
One thing that both Charles and Anne have in common is failed first marriages.
But before either wed, Anne is said to have had a romance with Andrew Parker Bowles, the first husband of the now Queen Consort Camilla.
However, it is said that their courtship did not overlap with Charles and Camilla's budding relationship.
But in the end, Anne wed first husband Mark Phillips, with whom she had her children Peter and Zara.
Eight years later, Charles married Diana, with speculation at the time that the then Princess of Wales and Anne did not get on - although it was branded as being "fairy stories" by the Princess Royal.
After Anne divorced Mark, she eventually married her now husband Vice Admiral Sir Timothy Laurence, while Charles went on to wed Queen Camilla.
There were rumours of a frosty start between the two women, however, according to body language expert Judi James: "With time and age though, the suggestion is that there has been a thawing between the two women and their body language now shows signs of quite strong rapport and even friendship."
Queen's final hours
When the late Queen entered her final hours on September 8 last year, at their mother's side were Charles and Anne.
Anne is often dubbed the hardest-working royal due to her ability to rack up a huge amount of engagements in a day.
The two older children of the late monarch managed to get to her side to say her final goodbyes, whereas their younger siblings Prince Andrew and Prince Edward were too late.
After the Queen's death, Anne issued a statement paying an emotional tribute to her mother, but also pledging her allegiance to her brother the King.
She said: "I am also so grateful for the support and understanding offered to my dear brother Charles as he accepts the added responsibilities of the Monarch."
Coronation reward
Meanwhile, now it appears Charles and Anne are tighter than ever after he offered her a starring role in the Coronation.
As Charles and Camilla ride in the Gold State Coach back to Buckingham Palace, Anne will lead the larger procession featuring 6,000 armed services personnel.
The privilege dates back to the 15th century in Tudor times when two officers - a Gold Stick and a Silver Stick, were placed close to the sovereign to protect him or her from danger.
Royal sources revealed how the King personally told his sister of his wish and how she was "incredibly honoured" to be handed the role.
They also revealed the King, 74, often leans on his trusted lieutenant Anne, 72, for advice and is a fan of her "no-nonsense attitude".
A well-placed palace source said: "The direction of the King’s decision is clear for all to see.
"He is rewarding the Princess Royal for her loyalty and her unwavering devotion to duty above all else.
"The King values his sister as a trusted lieutenant and this is the perfect example of such a relationship."
