Prince Charles became King at instant of Queen's death and will address the world shortly

Prince Charles will officially be proclaimed as King Charles III on Friday (September 9) following the death of Queen Elizabeth II, as per the documents that detail what will happen in the wake of the monarch's passing.

Queen Elizabeth II died peacefully at the age of 96 on Thursday (8 September) at her royal estate in Balmoral, Scotland.

She was surrounded by her family at the time of her passing.

The documents that detail the immediate aftermath of Queen Elizabeth II's passing are known as Operation London Bridge, or by its code-name London Bridge Is Down.

However, there are seperate plans if the Queen had died elsewhere, which is exactly what happened.

Operation Unicorn is the plan now underway for handling the Queen's death in Balmoral.

newsphoto/Alamy Stock Photo

The content of the plans in the wake of the death of the monarch has been a hot button topic over the years.

Rumours have swirled with details on what would happen when the Queen eventually died - and now we're about to find out the truth.

In 2021, Politico obtained access to documents explaining in granular detail what would occur upon her passing.

The report included plans that would be laid down for the now-King Charles.

Charles became King Charles III at the moment of his mother's death due to an old common law rule.

The law states that Rex nunquam moritur’, which translates as ‘the king never dies’.

Basically, what that means is that as of the Queen's final breath the role of sovereign transfers to the heir.

So, in this case, from Queen Elizabeth II to King Charles III. After that, the line of succession carries on as normally.

There is one slight change for Prince Harry's children, however.

The children of Prince Harry and Meghan Markle will now be entitled to be a prince and princess respectively in the wake of the death of Queen Elizabeth II, aged 96.

Now that Harry's father is officially King Charles III, Archie Mountbatten-Windsor and Lilibet ‘Lili’ Mountbatten-Windsor will have an HRH title.

The new titles for Prince Harry's children are thanks to rules set out by King George V in 1917.

Technically, as Archie and Lili are now the children of a son of a sovereign, the two little ones can now use the titles of prince and princess.

Xinhua/Alamy Stock Photo

Although Charles became King Charles III the moment his mother loosened her final breath, he still does need to be proclaimed as the new King.

This will happen the day after the monarch's passing, so on Friday at 10am local time.

The Accession Council will meet at St James’ Palace to take care of that little detail.

The Accession Council consists of senior government figures, Lord Mayors and High Sheriffs of the City of London, Realm High Commissioners, Privy Counsellors, Great Officers of State, and some high-ranking civil servants.

But that's just the first part.

The freshly-minted King Charles III will meet with just the Privy Council afterwards, although that doesn’t always happen straight away.

Britpix/Alamy Stock Photo

Next up, the proclamation of the new monarch will be read outside St James’ Palace and at the Royal Exchange in the City of London as well.

Next, comes the suspension of UK's Parliament for 10 days and the UK Prime Minister Liz Truss will meet with the King. But that’s all on the first day.

There's still a boatload of stuff that needs to take place before King Charles III can settle down on the throne and rule.

He will then travel all around the United Kingdom as per his requirements set out in Operation Unicorn/London Bridge.

He will meet with Commonwealth and world leaders, including Australian Prime Minister Anthony Albanese in the coming days.

And this is all before his mum's state funeral in 10 days time at Westminster Abbey.

There will be a committal service in St. George’s Chapel at Windsor Castle, and the Queen will be buried in the castle’s King George VI Memorial Chapel alongside her late husband, Prince Philip.