The Duchess of Cambridge was admitted to hospital in the early stages of labour at 6am London time.
Kate travelled with her husband, the Duke of Cambridge, in a car from the palace to St Mary’s hospital in Paddington, west London.
Kate is set to deliver the third in line to the throne in the hospital’s private Lindo wing, which is where both Prince William and Prince Harry were born.
There is a strong police presence at the hospital and the world’s media are on high alert awaiting the arrival of the royal baby.
The birth will be announced in royal tradition – it will be displayed on an easel at the front of Buckingham Palace, but will also be followed by an announcement on Facebook and Twitter before the media.