Some "History"
The history of the "Kingdom" of Redonda is shrouded in doubt and legend, and it is difficult to separate fact from fiction.
M. P. Shiel, an author of works of fantasy fiction, was the first person to ever mention the idea of the "Kingdom of Redonda" and that was in 1929, in a promotional pamphlet for a reissue of his books.
According to one of several different versions of the story, his father, Matthew Dowdy Shiell, a banker from Montserrat, claimed the island when his first son, Matthew Phipps Shiell, was born. Supposedly the father felt he could legitimately do this, because it appeared to be the case that no country had officially claimed the islet as territory. Sheill senior is also said to have requested the title of King from Queen Victoria, and as legend has it, she granted it to him as long as there was no revolt against colonial power. The son (originally named Matthew Phipps Shiell but later known as M.P. Shiel) was supposedly crowned on Redonda at the age of 15 by a bishop from Antigua.
However, the whole story appears to have originated decades later with the son, M.P. Shiel, a fantasy and science fiction writer best known for his 1901 novel
The Purple Cloud, and so it is possible that some, or most, or possibly all of the story of his being made king of Redonda, may in fact be pure invention.

Kingdom of Redonda from the South West
In any case, again according to one version of the story, M.P. Shiel in later life gave the title, and the rights of his work, to the writer John Gawsworth (Terence Ian Fytton Armstrong), who seems to have sold the title several times, due to permanent bankruptcy. Gawsworth in turn is considered to have bestowed the title, and the rights to his and Shiel's work, to Arthur John Roberts.
Roberts resigned his title in 1997 and named William Leonard Gates as his successor (and bearer of the rights of the work of both Shiel and Gawsworth).
A quote from King Juan II himself (according to King Robert the Bald):
“The legend is and should remain a pleasing and eccentric fairy tale; a piece of literary mythology to be taken with salt, romantic sighs, appropriate perplexity, some amusement, but without great seriousness. It is, after all, a fantasy."