William Lethbridge-Stewart was a member of the Lethbridge-Stewart family, a part of the Scottish Clan Stewart (TV: Terror of the Zygons) in the 16th and 17th centuries. He was related to the Stuart kings of Scotland and, subsequently, England, and a distant ancestor of Brigadier Alistair Gordon Lethbridge-Stewart.
A close advisor of King James VI of Scotland, Lethbridge-Stewart accompanied him to London in 1603 in preparation for his coronation as James I of England. Their arrival was triumphant, marked by what the Eighth Doctor called "a glorious parade, a magnificent spectacle." (PROSE: The Dying Days)