Réne-Louis de Voyer de Paulmy d'Argenson is better known to history as the Marquis d'Argenson due to his memoirs. When the Marquis was 23 years old (and still a Comte) he met a young lady who at the time went under the title of Marquise de Biron. That lady's name was Marie-Adélaide de Gramont and she was four years his junior.
Marie-Adélaide had been married at an early age to the Marquis de Biron and had then taken her place at court as a dame du Palais to Marie Leszczynska in 1725. The following year she and her husband were elevated to the rank of Duc and Duchesse de Biron although they were known as the Duc and Duchesse de Gontaut. On account of the Marquis d'Argenson himself (who describes her in his memoirs) their affair lasted for just year because he was obliged to leave on a political mission to Hainaut.
|The Marquis d'Argenson|
D'Argenson's memoirs leaves us with a vivid image of the Duchesse:
"She had a touching face, was sincere and full of feeling, constant, reasonable and generous; extremely seductive in a tête-en-tête..."
Rather surprisingly, the Marquis admits that the affair was instigated by her. This he did not attribute to any particular sense of coquetry but rather, that since she had been married at an early age, she was more experienced in love than him. Their affair seems to have ended amicably; once the Marquis left she took another lover - her husband having been dead some years - and eventually married him.
Whether the Duchesse continued to habour romantic emotions for her former lover is unknown but we do know that that was the case for him. His memoirs attest to the fact that he continued to love her even after her marriage - in his own words he "often regretted their rupture".
Even though their intimate affair lasted just a short while several letters of theirs survive which tells us that they had a special relationship for quite some years before that. The letters that survive dates from 1737 to 1740 - the year that Madame de Gontaut died.
Despite his regret - or perhaps because of it - he ceased to visit her in her house following her marriage. He himself did not exclude himself from female company; other mistresses followed his dear Madame G. If you are wondering why the Marquis did not marry the Duchesse himself there was a very good reason for that: he was already married.
In 1718 Réne-Louis had married Marie-Madeleine Méliand; her year of death seems disputed but one source puts it as late as 1781 - if true then she would have been very much alive when the affair took place.