The 96-year-old monarch is surrounded by family members who have travelled to be with her and is said to be “comfortable” by Buckingham Palace.
Her last public engagement was appointing Liz Truss as the new Prime Minister on 6 September.
The Queen ascended the throne in 1952 at just 25-years-old, following the death of her father, King George VI.
But who will succeed Queen Elizabeth II if she dies? Here’s everything you need to know.
Who will succeed Queen Elizabeth II?
Prince Charles will automatically become king after The Queen passes.
The Prince was previously married to Princess Diana from 1981 to 1996, the Princess died in 1997 following a car crash in Paris.
He is now married to Camilla, Duchess of Cornwall, with the pair tying the knot in 2005.
When Charles becomes king, Camilla’s official title will be Queen Consort.
Queen Elizabeth II confirmed the Duchess’ title during her Platinum Jubilee celebrations, Camillia was originally going to be given the title Princess Consort.
During the Queen’s 70th day Accession message she expressed her “sincere wish that, when that time comes, Camilla will be known as Queen Consort as she continues her own loyal service”.
Queen’s line of succession:
- Prince Charles, the Prince of Wales
- Prince William, the Duke of Cambridge
- Prince George of Cambridge
- Princess Charlotte of Cambridge
- Prince Louis of Cambridge
- Prince Harry
At 73-years-old, when Prince Charles accepts the position, he will be the oldest monarch ever crowned in British history.
Will Prince Charles be King?
Prince Charles will automatically become King after the Queen dies.
However, there has been speculation that Prince Charles will pass the title down to his first born son, Prince William, but this could only happen if Prince Charles decides to abdicate.
The last time a King abdicated was King Edward VIII, who renounced his title in 1936 to marry American divorcee Wallace Simpson.
According to experts at University College London’s (UCL) Constitution Unit if Prince Charles decided to abdicate, parliament would need to pass this with legislation.
The UCL the group said: “Under common law, Prince Charles will automatically become King the moment the Queen dies. Prince William could only become King if Prince Charles chose to abdicate.
“That would require legislation, as happened with the Declaration of Abdication Act 1936. The line of succession is regulated by parliament (as in the Act of Succession 1700, and the Succession to the Crown Act 2013); it can be changed only by parliament and cannot be unilaterally altered by the monarch of the day.”
What will Prince Charles be called?
If he takes the throne, it’s expected the Prince will take the title King Charles III.
The last time the UK had a King Charles was between 1660-1685.
His father, King Charles I was the only British monarch to ever be executed in 1649 by Oliver Cromwell.
However, Prince Charles could take another name as he has four.
Charles’ other names include: Philip, Arthur and George.
Can the Queen decide who takes the throne?
The Queen cannot decide who will take the throne after her death.
The line of succession is regulated by Parliament and the monarch has no control to change it.