(xi) The King of Ys combines historical fantasy based on French legends with historical fiction based on fourth century events whereas The Prisoner combines spy fiction, science fiction, satire and allegory.
(xii) Ys is a four volume prose narrative whereas The Prisoner is a seventeen episode TV series. (Prisoner episodes were made in three sets of four with a thirteenth to complete the first season. When it was decided that there would only be one season, a fourth set of four was made. Hence, seventeen.)
(xiii) Ys was a creative collaboration whereas the final form of The Prisoner resulted from a creators' disagreement.
(xiv) The Village is a secret installation and Ys is shrouded by a divine "Veil." Few go there and records get lost. Caesar visited but did not mention it.
(xv) Because its history is Veiled, Ys becomes a legend and the legend inspired the Andersons' tetralogy which explains the Veil! Legend, history and fiction merge. The Village became an iconic image although I have just met a younger person who had not heard of it.
(xvi) Although Gratillonius is King of Ys, he must engage in civic politics to get his policies accepted. Although No 6 is a prisoner, he defies successive No 2's, forcing the demotion of several.
(xvii) Gratillonius is important not only as King but also because:
the Queens summoned him;
he is an active and proactive King, not merely ceremonial;
he turns out to be the last King of Ys.
Sometimes No 6 seems to be just another prisoner but at other times the entire Village seems to revolve around him. Was it built for his benefit? Is he testing its security? He is elected No 2 but then shown that elected office is not real power. The Prisoner satirizes politics and the press.
(xviii) When Ys falls, Christ wins. The Prisoner makes no overt reference to religion but it might be a subtext. McGoohan's religious beliefs affected what he did on screen and there is some prophetic imagery.