A peer of France, brigadier, maréchal de camp, knight of the ordre du Saint-Esprit, he was chosen to be minister plenipotentiary to the Estates General of the Dutch Republic.

His mother, Marie Françoise de Béthune (1712–1799) was the daughter of the duke of Charost, who was governor to the king's person to Louis XV.

After the war he was made governor of Cognac and took advantage of the post to write and have published an elogy of Louis XVI's father, entitled Portrait de feu monseigneur le Dauphin.

[1] In 1776, on the recommendation of Vergennes, Louis XVI chose La Vauguyon to be France's representative to the Estates General of the Dutch Republic.

On his arrival, the Estates were in a sense under the control of the British government - when he left a solemn deputation from the Estates conveyed him their public recognition for his services and gratitude for the : constant zeal and illumination he had never ceased to show for the common interests of France and the [Dutch] Republic, praying him to be the organ of their recognition before his sovereign and to gain the honour of a defensive alliance[2]In 1784, La Vauguyon was made French ambassador to Spain.

Fearing he would pay for "the short and disastrous honour of his ministry"[4] with his head, he disguised himself as a businessman, took a passport under a false name and fled to Le Havre with his son in the hope of crossing to England.

[7] His time in the conseil d'État ended in February 1797 when, due to courtesans' intrigues, he fell into disgrace with the pretender, who his father had nicknamed "the disingenous".

Lacking ambition, he lived in great simplicity and was received as a member of the société d'instruction élémentaire, several times being elected its president and putting much zeal into spreading mutual education.

In his memoirs baronne d’Oberkirch writes that: France's envoy to the Hague was the duke of La Vauguyon, later ambassador, whose mother was a Breteuil.

At 3am she was walking with the duchess of La Vauguyon - these two masquers were accosted by a young foreign lord (a stranger to them) who unmasked and spoke for them with a long while, taking them for two ladies of quality of his acquaintance.

The two ladies witnessed to their desire to retire; the German baron led them; he presented a simple carriage to them; when he question them as they got in, madame de La Vauguyon unmasked.

She had much spirit but hid it for fear of exposing her dignity by showing it and of also compromising the superiority of Madame la comtesse de Provence.