Lord British
Lord British was the King of Britannia. He was played in-game by Richard Garriott, the creator of Ultima Online.
The fiction was that Lord British was somehow from the real world, as was the Avatar.
Lord British invented the Virtues.
Lord British disappeared for unknown reasons after Garriott left EA. He later returned around the time of the Age of Shadows expansion, for a plotline involving Minax. Garriott did not play Lord British for this return, but rather simply allowed UO to use the character on a temporary basis, to have some fictional explanation for the departed king. He left again in short order, in order to take a powerful artifact of some kind to the Ethereal Void to guard it from Minax.
In his stead, the realm is ruled by the Britannian Council, basically a Parliament of some kind, and or by the role-played High Councils that exist on various, but not all, shards.
http://en.wikipedia.org/wiki/Lord_British
http://ultima.wikia.com/wiki/Lord_British
