a grand old man of
the grand old man of (something)
The most senior and respected man in a particular organization, society, etc. His decades of hosting charity balls and galas have made him the grand old man of London.
a (or the) grand old man ofa man long and highly respected in a particular field.
Recorded from 1882 , and popularly abbreviated as GOM, Grand Old Man was the nickname of the British statesman William Ewart Gladstone ( 1809–98 ), who went on to win his last election in 1892 at the age of eighty-three.