'Captain-General' is a title of honour, the holder of which takes precedence over all Colonels Commandant. Duties are mostly of a ceremonial or social character.
Originally the Office was called 'Colonel of the Royal Artillery'. In 1865 when the Commander-in-Chief, HRH The Duke of Cambridge, held it the title was changed to 'Colonel-in-Chief of the Royal Artillery'. Then in 1950, HM King George VI expressed the wish that the Office be re-designated 'Captain-General of the Royal Regiment of Artillery'.
HM Queen Elizabeth II accepted the Office in 1953.