Queen Elizabeth died of old age.
The British monarch passed away on 8 September at the age of 96 and her death certificate has now been released into the public record, with the cause of death simply listed as "old age".
Although the news of the queen's passing wasn't made public until around 6.30pm, the entry into the National Records of Scotland - which was signed by the monarch's daughter, Princess Anne - revealed she actually passed away at 3.10pm.
This means that a number of the queen's relatives, including her sons Prince Andrew, Prince Edward, daught-in-law Sophie, Countess of Wessex, and Prince William, were still travelling to her Balmoral Estate in Scotland when she died.
A private plane carrying the quartet took off from RAF Northolt at 2.39pm and landed in Aberdeen, around an hour away from the estate, at 3.50pm.
William's brother, Prince Harry, arrived a few hours later on a separate flight.
As well as Anne, the queen's son, the new King Charles, was also by his mother's side when she passed away.
Over the weekend, Buckingham Palace released a photo of the queen's final resting place.
The monarch was buried in The King George VI Memorial Chapel at Windsor Castle on September 19, and the ledger stone marking the site shows her name inscribed in gold lettering, alongside her parents, Queen Elizabeth the Queen Mother, King George VI and her late husband Prince Philip.
Alongside the image, a post on the royal family's Twitter read: "A ledger stone has been installed at the King George VI Memorial Chapel, following the interment of Her Majesty Queen Elizabeth.
"The King George VI Memorial Chapel sits within the walls of St George’s Chapel, Windsor."
The ledger stone also includes the names and dates of birth of each of the royals.
Buckingham Palace previously confirmed that the late monarch was laid to rest alongside Prince Philip, who died in April 2021, aged 99.
A statement on the royal family's website read: "The Queen was buried together with the Duke of Edinburgh, at The King George VI Memorial Chapel."