 At Soleure, in November 1790, he received from Louis XVI exclusive powers to negotiate with the European courts, and in his efforts to check the ill-advised diplomacy of the "émigré" princes, he soon brought himself into opposition with his old rival Calonne, who held a chief place in their councils.In coordination with Marie Antoinette's favourite, the Swedish count Axel von Fersen, Breteuil organised the royal family's escape from Paris in 1791, garnering support from King Gustavus III of Sweden.The attempt almost succeeded, but was foiled at the last minute by Jean-Baptiste Drouet, the Republican son of a local postmaster.