The British monarchy's rules state that "a new sovereign succeeds to the throne as soon as his or her predecessor dies".
That means Queen Elizabeth II's eldest son, Prince Charles, became king immediately upon her death.
However, it may be months or even longer before Charles' formal coronation. In Elizabeth's case, her coronation came on June 2, 1953 - 16 months after her accession on February 6, 1952, when her father, King George VI, died.
A look at the formalities that take place after Charles accedes to the throne: