A/the grand old man - Idioms by The Free Dictionary
a/the grand old man
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/the ˌgrand old ˈman (of something) an old man who is very experienced and respected in a particular profession, etc: At eighty, he is the grand old man of the British film industry.