'Their Royal Highnesses The Duke and Duchess of Cambridge are very pleased to announce that The Duchess of Cambridge is expecting their third child. The Queen and members of both families are delighted with the news,' it read.
'As with her previous two pregnancies, The Duchess is suffering from Hyperemesis Gravidarum,' the statement continued. 'Her Royal Highness will no longer carry out her planned engagement at the Hornsey Road Children’s Centre in London today. The Duchess is being cared for at Kensington Palace.'
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The Duke and Duchess's last public event was as recent as last Thursday, when the duo visited William's late mother Princess Diana's memorial gardens at Kensington Palace to mark 20 years since her death. It is believed that the news of Kate's pregnancy has been released early, due to her illness preventing her from fulfilling today's engagement.
In Manchester this afternoon, Prince Harry reacted to the news saying it was, 'fantastic, great. Very, very happy for them.'
The royal couple are already parents to 4-year-old son Prince George and 2-year-old daughter Princess Charlotte. George is due to start primary school at Thomas's Battersea on Thursday. Last week, the couple announced that they would be accompanying George for this important milestone, but it is unclear whether Kate's illness might affect this.
'The Duke and Duchess of Cambridge, accompanying Prince George, will be met on arrival at the school by the Head of Lower School, Helen Haslem, who will then escort Their Royal Highnesses to Prince George's reception classroom,' the statement said.
The arrival of this new sibling could be an historic one. If the baby is a boy, he will not overtake elder sister Charlotte in the line of succession thanks to a law passed before the birth of their first child George. The new rule means that boys no longer take preference over girls.
The Duke and Duchess have made no secret about their plans for a third child, with Kate recently joking on their royal tour of Germany that they would have to have 'another one' when a well-wisher presented them with clothes for a newborn. She is also one of three, with younger sister Pippa (who recently wed financier James Matthews) and brother James. As recently as two days ago, the media were reporting that sister Pippa might also be pregnant.
This is the first time in a generation that there has been more than two siblings in a direct branch of the royal family. The Queen had four children - Charles, Anne, Andrew and Edward - but each of them only had two children, William and Harry, Peter and Zara, Beatrice and Eugenie, and Louise and James, respectively.
Congratulations to the happy couple!