As the UK's head of state, King Charles has number of parliamentary and constitutional duties.
How the line of succession passes through generations of the Royal Family
The photo shows William and Catherine lying in grass with their children, Prince George, Princess Charlotte and Prince Louis.
The footage was filmed by photographer Matt Porteous in Cornwall earlier this month.
A post shared on Kensington Palace's social media reads: "Wishing everyone a very Happy Christmas."
The Prince and Princess of Wales have shared new photos of Prince William with George, Charlotte and Louis.
A photograph taken in Norfolk this month has been released to mark the birthday of Prince Louis.
Prince George, Princess Charlotte and Prince Louis post a Father's Day tribute to Prince William in their first social media post.
William and Catherine release the photograph a week after doing the same for their youngest son, Louis's birthday.
