The 73-year-old is the oldest King to assume the throne, (before him it was William IV who was the oldest when he became King at the age of 64 back in 1830) and also is the oldest and longest-serving heir in British history.
As a result of becoming King Charles III, he is also now the Defender of the Faith and Supreme Governor of the Church of England.
“It always seems to me that while at the same time being Defender of the Faith you can also be protector of faiths," Charles has said about the title in 2015.
The Duchy of Lancaster is the private estate of the British sovereign and plays a major role in the monarch's income which King Charles III inherited from the Queen as well as the custom title of the Duke of Lancaster.
Camilla - Queen Consort
Britain's Camilla, Queen Consort, greets the members of the public in the crowd upon her arrival at Buckingham Palace in London, on September 9, 2022Photo by BEN STANSALL/AFP via Getty Images
Ahead of Camilla's nuptials to Charles in 2005, it was thought Camilla would have taken up the brand-new title of Princess Consort.
However, the Queen made it clear during her Platinum Jubilee celebrations, her wish for Camilla to become the Queen Consort and in an open letter back in February 2022, she wrote:
"And when, in the fullness of time, my son Charles becomes King, I know you will give him and his wife Camilla the same support that you have given me; and it is my sincere wish that, when that time comes, Camilla will be known as Queen Consort as she continues her own loyal service."
Camilla is Queen Consort like the Queen Mother was and cannot be Queen Regnant because she does not rule in her own right, like Elizabeth II did.
As Queen Consort, Camila will be referred to as Her Majesty instead of Her Royal Highness.
Prince William - Princes of Wales
Prince William is now the Duke of Cornwall and Cambridge, but not the Prince of WalesPhoto by CHRIS JACKSON/POOL/AFP via Getty Images
Prince William is the eldest child of King Charles III and was known as the Duke of Cambridge.
But since the Queen's passing, the heir to the throne will now be known as the Prince of Wales, taking on a title his father previously held.
Consequently, William is thought to inherit the Duchy of Cornwall - a 150,000-acre estate which has an annual income of £20m.
Alongside this he also has new Scottish titles: Duke of Rothesay, Earl of Carrick, Baron of Renfrew, Lord of the Isles and Prince and Great Steward of Scotland.
The Prince of Wales title was not automatically passed down to William but Charles decided to hand this title to his son.
Catherine Middleton - Princess of Wales
Kate Middleton will now be known as the Duchess of Cornwall and CambridgePhoto by Chris Jackson/Getty Images
When Kate Middleton married Prince William in 2011, she also became the Duchess of Cambridge, and like her husband, her title has now changed following the Queen's passing.
She will now be known as the Princess of Wales and is also the Duchess of Rothesay in Scotland, inheriting the title previously held by Camilla.
Prince George (left), Prince Louis (middle) and Princess Charlotte (right) with their parents, the Duke and Duchess of Cornwall and CambridgePhoto by Jonathan Brady - Pool/Getty Images
The children of Prince William and Kate Middleton - George, Charlotte, and Louis will also be styled like their parents and will be known as Prince George of Cornwall and Cambridge, Princess Charlotte of Cornwall and Cambridge, and Prince Louis of Cornwall and Cambridge.
If Charles gives William the Prince of Wales title, the children would be "of Wales."
Prince Harry & Meghan Markle
Prince Harry and Meghan Markle's title do not changePhoto by Chris Jackson/Getty Images for Invictus Games Dusseldorf 2023
Prince Harry and Meghan Markle's title of the Duke and Duchess of Sussex has not changed due to the Queen's passing, and they no longer use HRH titles after they stopped their royal duties back in 2020.
Archie & Lilibet
Archie Mountbatten Windsor with his parents the Duke and Duchess of SussexPhoto by Toby Melville - Pool/Getty Images
The children of Prince Harry (who is fifth in line to the throne) and Meghan Markle, Archie and Lilibet "Lili" Mountbatten Windsor are now technically a prince and princess.
So their names would be HRH Prince Archie of Sussex and HRH Princess Lili of Sussex.
Previously, the children were too far down the line of succession for these titles but now they are a son (and daughter) of a son of a sovereign, they both can be HRH and be a prince and princess according to the rules set out by King George V in 1917.
However, if Charles wanted to curb the number of royals and change Archie and Lili's right to be a prince and princess, he would have to issue a Letters Patent to amend this.
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