Question: In what year was the last monarch under which Robert Waterton was a trusted servant of the House of Lancaster born?
Sentence (from "Lucius Petronius Taurus Volusianus"): The nature of his relationship to the Licinii is uncertain, but it seems likely that a common origin in the Etruscan region of central Italy predisposed Gallienus at least in his favour and he seems to have been that prince's most trusted servant and adviser during the period of his sole reign - 260(?)
Relevant evidence: No