The image was shot by photographer Matt Porteous during the family's Easter break in Cornwall.

A separate video from the same holiday was posted hours later, in which Charlotte can be seen bowling a cricket ball, patting the family's dogs Orla and Otto and using white shells to write a message in the sand. Sharing the short montage on social media, Kensington Palace wrote: "Thank you for the lovely birthday messages for Princess Charlotte, 11 today!". On Wednesday, Prince William and Princess Catherine also shared a new family portrait, as they marked 15 years of marriage.

In the photo, William and Catherine are seen lying in the grass, smiling, with their children - Prince George, Princess Charlotte and Prince Louis - and their two dogs, Orla and Otto, during the Easter break. The photographs were taken by Porteous during their time in Cornwall. Porteous, who is based in Jersey, has received royal commissions in the past from Prince William and Catherine, including for behind the scenes moments from Louis' christening, Christmas cards and royal portraits.

Charlotte's birthday portrait and video comes just a day after the Wales' celebrated the first birthday of their second dog, Otto. They shared a photo of the brown spaniel who is sitting in a grassy field in Cornwall, with the caption: "Welcome to the family, Otto! 1 today".

Princess Charlotte - formally known as Her Royal Highness Princess Charlotte of Wales - was born 08:43 on 2 May 2015 at St Mary's Hospital in Paddington. As the granddaughter of King Charles, she is third in line to the throne. She has two brothers, Prince George, 12 and Prince Louis, 8. The Princess was last seen in public at the Royal Family's annual Easter Sunday church service in Windsor, where she was smiling and waving at crowds. (BBC)