Edward II's queen Isabella of France, then eighteen years old, visited her homeland in March/April 1314 to petition her father Philip IV on some matters concerning her husband's duchy of Gascony. Isabella arrived in Paris on 16 March 1314, the day after her father had Jacques de Molay, Grand Master of the Knights Templar, and his deputy Geoffrey de Charnay burned alive on an island in the middle of the River Seine. The queen returned to England in late April 1314, just after Edward II's thirtieth birthday.
It is probable that while she was in France, Isabella discovered that Marguerite and Blanche of Burgundy, respectively the wives of her eldest brother Louis, king of Navarre (then aged twenty-four) and third brother Charles, count of La Marche (nineteen going on twenty), had been conducting extramarital affairs with the d’Aulnay brothers, Philip and Gautier, and informed her father. It is not certain that she did, but several fourteenth-century chroniclers thought that she had, and it would perhaps be a little too much of a coincidence that she just happened to be in Paris at the time that the scandal broke. On 6 April 1314, a payment was made to several boys carrying torches who escorted Isabella after dark to her father’s palace on various occasions, which, although it may of course have been entirely innocent, certainly sounds rather cloak-and-dagger. Whether Isabella did tell her father or the news came out in some other way, it transpired that Queen Marguerite and Countess Blanche had been meeting their lovers at the Tour de Nesle, a tower in Paris, where they had dined with the d’Aulnay brothers and afterwards committed adultery with them. Joan of Burgundy, older sister of Blanche* and wife of Isabella’s second brother Philip of Poitiers, was not accused of having a sexual affair with anyone, though did apparently know what was going on and ineffectually begged the women to stop, but did not tell anyone. Joan was temporarily imprisoned in 1314 but released after her father-in-law’s death later that year. She remained married to Philip for the rest of his life, and was queen-consort of France between 1316 and 1322. On the death of her mother Mahaut, she inherited the county of Artois, and had already inherited the county of Burgundy from her father.
* Joan (b. 1287/88) and Blanche (b. 1295/96) of Burgundy were the daughters of Othon IV, count of Burgundy, and Mahaut, countess of Artois in her own right. The county of Burgundy was also known as the Franche-Comté. Marguerite of Burgundy (b. 1290) was the daughter of Robert II, duke of Burgundy, and Agnes of France, youngest daughter of Saint Louis IX. Marguerite was thus a first cousin of her husband's father Philip IV. Her younger sister Joan, b. c. 1293, married Isabella of France's first cousin Philip of Valois and became queen-consort of France in 1328. (Which means that there was Philip V of France and his wife Joan of Burgundy, and his cousin Philip VI of France and his wife Joan of Burgundy. Nope, not confusing at all!)
If Isabella did break this scandal, as a few chroniclers claim she did, her motives were almost certainly not vindictive. She was the daughter of two sovereigns and had been raised with a sacred sense of royalty, and therefore, would have been profoundly disturbed at the notion that her sisters-in-law might foist a child not of the royal bloodline onto the French throne. In my opinion, though some historians have questioned the truth of the story, there is little doubt that Marguerite and Blanche of Burgundy were indeed sleeping with the d’Aulnay brothers. The severe punishment meted out to the two women (perpetual imprisonment) and the d’Aulnays (grotesque execution) suggests that the evidence against them was undeniable. Philip IV would not have imprisoned his first cousin Marguerite of Burgundy, whose royal mother and Philip’s own aunt Agnes of France was still alive, and proclaimed two of his sons as cuckolds before the whole of Europe, had he not been certain of Marguerite and Blanche’s guilt. A rather later and mostly unreliable French chronicler claims that Isabella spotted what was going on when she gave her sisters-in-law a gift of purses during her and Edward’s visit to Paris in the summer of 1313, and on her second visit in 1314 saw the d’Aulnay brothers wearing them. The story may (or may not) have some truth in it, but Philip IV would have required far more compelling evidence than this to imprison a woman who was Saint Louis IX’s granddaughter, the crowned and anointed queen of Navarre and the duke of Burgundy's sister.
Marguerite and Blanche of Burgundy, weeping, their heads shaved, were sentenced to life imprisonment in Château Gaillard, the grim and forbidding fortress in Normandy built in the 1190s by King Richard Lionheart of England. Their lovers suffered a far worse fate: they were castrated and their genitals thrown to dogs, flayed, and broken on the wheel, before decapitation mercifully put an end to their dreadful torment. The later English chronicle Scalacronica claims that one of the brothers escaped to England, but was captured in York and sent back to France, though the story is unconfirmed by any other evidence. Blanche of Burgundy was only about eighteen or nineteen in 1314, and had given birth to her son Philip – who died as a child a few years later – mere weeks before her arrest. The marriages of Louis and Marguerite and Charles and Blanche were not annulled; Louis had to wait until Marguerite’s death in August 1315 before he could marry again, and Charles remained married to the captive Blanche until September 1322, after he succeeded to the French throne and finally managed to persuade Pope John XXII to annul their marriage. Even then, annulment was granted on the grounds of spiritual affinity, as Blanche’s mother Countess Mahaut of Artois was Charles’ godmother, and not because of Blanche’s adultery. Blanche of Burgundy was finally released from prison in 1325 and died, her health broken, sometime in late 1325 or early 1326, still aged only thirty. Marguerite of Burgundy became queen-consort of France, at least in name, on the death of her father-in-law Philip IV in November 1314, but was never crowned or acknowledged as such. She died on 15 August 1315 at the age of twenty-five, either murdered or as the result of harsh treatment during her incarceration. Her only child succeeded as Queen Joan II of Navarre at the age of sixteen in 1328, married her cousin Philip of Evreux, and was the mother of Charles 'the Bad', king of Navarre and count of Evreux. Herr widower Louis X of France and Navarre married his second wife Clemence of Hungary four days after her death.