As tutor and a principal adviser to the young George III; John Stuart was able to establish and maintain a position in British politics for a number of years, including a brief tenure as Prime Minister from 1762-63. Even in retirement he was reputed to secretly influence the government through his position as confidant to the king. He also introduced the Scottish painter Allan Ramsay to George III, a relationship which developed into establishing Ramsay as the principal court painter in Britain in the late eighteenth century.