Pierre Michel Hennin (1728-1807) is not the most famous of Chabanon’s contemporaries. The two men met in Geneva, when the resident of the king of France, who counted Chabanon among his table companions, was seeing Voltaire on a regular basis. In a politically tense climate, the two men, both in their thirties, built up a friendship in the merry company moving around Ferney. That relationship has come down to us thanks to the correspondence they kept for eight years, and which is now preserved in the Hennin collection. The negotiator was indeed a prolific letter-writer, with various and numerous correspondents, who took into account all sociability parameters to appear as an indispensable participant on the political scene, as a cultural mediator and as a propagator of the Enlightenment. Playing for time with Voltaire’s interventions in the Geneva affairs, he built up his persona as an informed and level-headed diplomat. His quest for professional recognition went hand in hand with his ambition as a learned and erudite collector, who still had to wait for the consecrastion of the Academy.