past master

noun

the manager was a past master at recharging faltering spirits:

expert, virtuoso, master, wizard, genius, artist, old hand, adept, professional, doyen, veteran, maestro, connoisseur, authority, grandmaster, master hand, skilled person;

informal ace, buff, pro, star, whizz, hotshot, ninja;

British, informal dab hand;

North American, informal maven, crackerjack.

past master Oxford Dictionary of English