William V

William V was the king of the United Kingdom who succeeded Charles III. When the Tenth Doctor found that Edward VII had disappeared along with Balmoral Castle in 1902, he warned that the future of the royal family, along with the rest of history, was threatened, saying that, along with the rest of his successors, there would be no William V. (PROSE: Revenge of the Judoon)

During the Martian Invasion on 6 May 1997, which fell within the reign of Queen Elizabeth II, the Prince of Wales and his sons were on the royal jet on course to London when the Martian ship entered the atmosphere, diverting to Madrid. (PROSE: The Dying Days)

A member of the Silence was present at his wedding to his wife during the reign of Elizabeth II. (PROSE: The Secret Lives of Monsters)

Searching through the pocket of the Ninth Doctor's leather jacket, Rose Tyler found a £10 coin which claimed to show the head of William V. (PROSE: Winner Takes All)

Behind the scenes

 * In the real world, William became the heir to the British throne, and the Prince of Wales, in 2022, when his grandmother Queen Elizabeth II died and his father Charles III (the former Prince of Wales from 1958-2022) became King. This happened 14 years after the publication of Revenge of the Judoon and three years after the book's author Terrance Dicks died.
 * He is the elder brother of Prince Harry.