Aethelred

Aethelred was the chief administrator of the leisure planet Caligaris Epsilon Six in 7711. Despairing of what he saw as the breakdown of the Third Great and Bountiful Human Empire, he decided to isolate Caligaris Epsilon Six by means of a planetwide quarantine and set himself up as its king. All adult inhabitants of the planet were killed by recombinant yersinia pestis; the children who survived the disease unquestioningly accepted "King" Aethelred's explanations.

Aethelred was deposed 150 years later, with the help of the Eleventh Doctor and Amy Pond. (IDW:A Fairytale Life)