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
It's a big year for the young prince, who will start secondary school at the elite Eton College in September.
The Princess of Wales congratulated Arthur Fery on his run to the semi-finals and wished him a happy birthday.
How much attention did you pay to what happened in the world over the past seven days?
The prince is set to attend the elite boarding school from September, Kensington Palace has announced.
He will follow in the footsteps of his father, the Prince of Wales, who also attended the private school.
The photo shows William and Catherine lying in grass with their children, Prince George, Princess Charlotte and Prince Louis.
A post shared on Kensington Palace's social media reads: "Wishing everyone a very Happy Christmas."
