Charles III

Charles III, formerly known as Prince Charles, was the king of the United Kingdom who succeeded Elizabeth II. Charles reigned with his Queen, Camilla, and was succeeded by William V. (PROSE: Revenge of the Judoon)

Marriage to Diana
In 1981, (TV: The Lodger) he married Princess Diana. (PROSE: Prisoners of the Sun) Melanie Bush believed them to be a strong couple. (AUDIO: Spaceport Fear)

He was photographed during his wedding to Diana. Said picture was altered by the Monks during the 2017 Monk invasion. (TV: The Lie of the Land)

With Camilla
Charles and Camilla were popular items of gossip in 2005. (AUDIO: One Rule)

By 2010, he had married Camilla. In that year, Clyde Langer and Rani Chandra faced two Automatons who were looking for the estranged crown prince of their homeworld. Clyde jokingly offered them to take Prince Charles and Camilla as a replacement. (TV: The Empty Planet)

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 Charles III. (PROSE: Revenge of the Judoon)

As King
His mother, Elizabeth II, assumed in 1977 that Charles would be King by 2022, before learning, to her amazement, that she would be celebrating her seventieth year on the throne in that year. (PROSE: The Platinum Sceptre) However, according to another account, the British Army had a group called the King's New Delta Squadron by 2020. (AUDIO: Black and White)

Upon seeing the Council House of Kirith, the Seventh Doctor wondered what King Charles would have to say about its blend of architectural styles. (PROSE: Timewyrm: Apocalypse)

Legacy
Charles III was immediately succeeded by King William V. (PROSE: Revenge of the Judoon)

Charles Windsor Griffiths was named after him. (PROSE: Attack of the Cybermen)

Alternate timeline
In an alternate timeline briefly created by Jamie McCrimmon in which the Glorious Revolution of 1688 was a failure, Charles III was not the successor of Elizabeth II, but the grandson of James II, Bonnie Prince Charlie, who was the reigning monarch of England and Scotland in 1788. (AUDIO: The Glorious Revolution)

Behind the scenes

 * In the real world, Prince Charles is the son of Queen Elizabeth II and Prince Philip, and heir apparent to the throne.
 * When a heir accedes to the British throne, he or she may choose the name they will rule under, and it does not necessarily have to be their birth name. There is no guarantee that when Charles takes the throne in real life that he will, in fact, choose to be Charles III.
 * A recurring way of indicating it's the near future is to have a King (Charles) instead of Queen Elizabeth: this was the idea behind Battlefield and "the King" is briefly mentioned in AUDIO: The Longest Night.
 * Charles has been portrayed by Christopher Bowen in the telefilm Princess in Love, Paul Rhys in the docudrama The Queen, Tim Piggott-Smith in the play King Charles III and its television adaptation, Jon Culshaw in various comedy sketches, Josh O'Connor in the Netflix series The Crown, and was voiced by Dan Stevens in the animated series.
 * In 2013, Charles and Camilla paid a visit to the TARDIS set at BBC Wales' Roath Lock studios where they met Matt Smith and Jenna Coleman as well as posing with Daleks and Cybermen.