The heir to the throne traditionally holds the title of Prince of Wales, but it isn't an automatic title.
Prince Charles has been heir to the throne since 1952, but he only received the Prince of Wales title from the Queen in 1958.
Prince William is widely expected to be the next Prince of Wales as the eldest son of Prince Charles.
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But whether or not this is the case will be a matter for Prince Charles as King and, while unlikely, he can technically decide not to grant William the title. The Queen granted King Charles the title in 1958.
However, William will automatically become the Duke of Cornwall and the Duke of Rothesay in Scotland when his father ascends the throne. He and Kate are now officially known as the Duke and Duchess of Cornwall and Cambridge.
Similarly, when William is King, it will also be his decision whether he grants the Prince of Wales title to his eldest child Prince George.
The Prince of Wales title is controversial as the last Welsh Prince of Wales, Dafydd ap Gruffydd, was brutally killed on the orders of Edward I of England in 1283.
The title has since been conferred by English and later British monarchs on their heirs, the most recent before Prince Charles being Prince Edward, the future King Edward VIII and Duke of Windsor after his abdication in 1936.
What is the Investiture of the Prince of Wales?
The investiture of the Prince of Wales is the ceremony formally acknowledging a new Prince of Wales. The prince is presented and invested with the insignia of his rank and dignity, in the manner of a coronation. An investiture is purely ceremonial.
What the ceremony looks like?
In the 1969 ceremony the Queen gave Charles the symbols that marked him as Prince of Wales; the sword, coronet, ring, rod and mantle. In addition to the 4000 guests present in the castle, 19 million watched on TV in the UK at home and another 500 million watched around the world.
Where will William be invested?
In 1911, the future King Edward VIII was invested in Caernarfon Castle. The present Prince of Wales, Prince Charles, was also invested there in 1969.
There is no suggestion that Caernarfon would host William's ceremony but the Prince does have connections to the area having lived and worked in Anglesey where he trained with the Royal Air Force while living with then girlfriend Kate MIddleton.
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