It is not wrong to say that no heir, in the history of the royal family, has prepared for the crown longer than King Charles III who ascended to the throne at the age of 73 after the death of his mother Queen Elizabeth II last year in September.
Charles become hair to the throne at the age of 3 when his mother was crowned as monarch in 1952. She was 27.
Since Queen Elizabeth's death at age 96, many have wondered whether Charles will abdicated the throne for his eldest son William.
At the time of Queen's passing, there were rumours and speculations that Charles would step a side as his mother wanted William to become king. But it does not seem true as in April 2018, Queen Elizabeth made the rare move of publicly backing Charles as future king as she formally asked the Commonwealth Heads of Government to appoint Charles as her successor of the association of Britain and its former colonies.
Even if she had desired to skip her eldest son, Charles, in favour of her grandson, William, she did not have the power to choose her successor on a whim.
Asper reports, the 1701 Act of Settlement is the act of Parliament that determines the succession to the throne and requires that a monarch's heir must be his or her direct successor (and a Protestant). That's Charles, not William.
The late monarch did not even have power to change a law instead, it could have to be taken up in Parliament, and it wouldn't be a quick and easy process.
In short, the Queen always wanted her son to take the throne, and at her Jubilee, she asked the nation to support Camilla as Queen Consort when Charles becomes the monarch.