Kesington Palace has announced that the Duke and Duchess of Cambridge are expecting a third child.

The announcement was made as Kate Middleton was forced to cancel an engagement on Monday, because of extreme morning sickness.

In a statement, Kensington Palace said: “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.

“As with her previous two pregnancies, the duchess is suffering from hyperemesis gravidarum. 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.”

The announcement comes as four-year-old Prince George is due to start school at Thomas’s Battersea, south London. Princess Charlotte is two.