Query: When did Burke become the Prime Minister's private secretary?
Context: When Hamilton was appointed Chief Secretary for Ireland, Burke accompanied him to Dublin as his private secretary, a position he held for three years. In 1765 Burke became private secretary to the liberal Whig statesman, Charles, Marquess of Rockingham, then Prime Minister of Great Britain, who remained Burke's close friend and associate until his untimely death in 1782. Rockingham also introduced Burke as a Freemason.