The monarch, who is awaiting the arrival of her third great-grandchild, left Windsor Castle to return to her London residence on the day that Kate Middleton went into labour.
It is at Buckingham Palace that the birth of Prince William and Kate's first-born will be announced.
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Once the little Prince or Princess arrives, a royal aide will leave the main entrance of the Lindo wing at St Mary's hospital, Paddington with a medical bulletin signed by the Duchess's doctors at birth.
The announcement will be taken to the palace by car accompanied by police and will be placed on a wooden frame on an easel behind the railings on Buckingham Palace.
It is expected that the bulletin will confirm the sex and weight of the baby but no other details. Once the announcement is posted on the easel, Kensington Palace spokespeople will confirm the details to press via an email.
Members of the Middleton family and the royal family including the Queen will be given this information before it is announced publicly.
The 88-year-old monarch said last week that she was hoping the baby would come before she went on her annual summer break to Balmoral in Scotland.
While the excitement among the press pack and the crowd of well-wishers gathered outside the Lindo wing reaches on all time high, the most recent update from the mum-to-be on Monday morning was that are 'progressing as normal'.
Kensington Palace confirmed the news early on Monday morning, revealing that the Duchess had travelled by car from Kensington Palace to the Lindo Wing with her husband by her side.
At around 6am on Monday, a royal convoy was spotted arriving at the hospital's rear entrance, and at 7.30am the statement was issued confirming the news the world has been waiting for.
The nation must now patiently await the arrival of the royal baby, which will be delivered by the Queen's former gynaecologist Marcus Setchell and the Queen's current gynaecologist Alan Farthing.
It is highly unlikely that there will be any updates during the labour stages, with the first sign that the child has been born being the exit of a royal official from the Lindo wing.
Watch all the action from outside the Lindo Wing as the world awaits news of the arrival of the Prince or Princess