Complex sentence: He was Private Secretary to the Duke of York 1933-1936, and Deputy Comptroller 1936, and when the Duke became King was appointed to his Household was Groom of the Robes 1937-1954.
Split into simpler sentences: He was Private Secretary to the Duke of York 1933-1936, and Deputy Comptroller in 1936. When the Duke became King, Campbell was appointed to his Household as Groom of the Robes 1937-1954.