Between 1702 and 1793, eleven men held the position of Agent General of the French Navy and Commerce in Madrid, created after the accession of the Bourbon Philip V to the Spanish throne. Acting without official status, at the interface between business and politics, these envoys of the Secretary of State for the Navy were the keystone of the French consular network in the Peninsula, and the true architects of Franco-Spanish commercial diplomacy in the 18th century. Informers, negotiators and mediators, these intermediaries in contact with the political and economic powers worked towards commercial rapprochement between the two monarchies, while seeking to reconcile sometimes contradictory merchant and princely interests. They examine the growing interaction between trade, economic expertise and international relations in the modern era, as well as the path that led from information to negotiation, from diplomacy from below to discussion between governments.