In November of that year he left Turin to make his first long journey, accompanying the Marquis Caraccioli, an ambassador from Naples who was moving from a post in Turin to one in London. Lagrange arrived in Paris shortly after his entry had been received but took ill while there and did not proceed to London with the ambassador.
Sa Nobyembre ng taon na siya kaliwa Turin upang gumawa ng kanyang unang mahabang paglalakbay, kasamang ang makwis Caraccioli, ng isang kinatawan mula sa Naples na ay lumilipat mula sa isang post sa Turin sa isa sa London. Lagrange dumating sa Paris sa ilang sandali lamang matapos ang kanyang entry had been natanggap ngunit kinuha habang may masama at hindi magpatuloy sa London kasama ang kinatawan.