My previous essay on the case for the defence deliberately did not address the grounds to suppose that there was some kind of plot against him. That is a whole other topic which needs to be examined in some detail. The motives of his enemies were not wholly financial, as simplified accounts of the life of Gilles de Rais often imply; politics also featured heavily.
However, the initial impetus behind the machination was property, as Bourdeaut grasped when he titled his book Chantocé, Gilles de Rais et les ducs de Bretagne. Gilles came into the world as a result of politicking over the border castles of Champtocé and Ingrandes and died for the same reason. Jeanne La Sage needed an heir urgently because she was a lone woman and therefore prey to any predatory noble. And Jean IV, the father of Gilles' nemesis, had long coveted the Rais estates, and those two castles in particular. They were of huge strategic importance, controlling ingress to Brittany by river, but they were also highly lucrative. Their lord could tax the river traffic; Jean de Craon's battles with the Loire boatmen lived on long after him in the form of various lawsuits. Gilles hung on to Champtocé almost until the end, not (as is sometimes suggested) out of sentimentality about his birthplace, but because the revenue it accrued was a welcome source of cold cash.
Brittany was, at this point, effectively bankrupt. At one point the Duke misappropriated the money his late wife had left to have masses said for her soul, because he was lacking in both money and morals. The Rais estates must have looked tempting. In fact, they were so alluring that they were confiscated a good fortnight before Gilles was even arrested: as Reinach remarks, when you give away the bearskin before the hunt starts, it means you have firmly resolved to kill the bear, by fair means or foul. (Quand on cède ainsi la peau de l'ours, c'est qu'on est bien décidé, per fas et nefas, a tuer l'ours.)
Most biographers argue that, since Jean V had obtained the two castles he particularly craved in early 1438, he had no reason to plot against Gilles to seize the rest of his estates. There is a muddled belief that Gilles was virtually bankrupt and no longer had anything worth stealing. Nothing could be further from the case. In order to acquire the estates he wanted, the Duke had had to exchange them for the entirety of the barony of Rais, which Gilles had sold previously. That was how valuable those particular estates were to Brittany. Once acquired, however, it was by no means certain that Jean V could hold on to them. According to Breton law, the Duke was not allowed to enter into property transactions with his vassals. For this reason he used proxies such as "Jean Pain" and, notoriously, Geoffroy Le Ferron. Champtocé was ostensibly bought for one of his sons. In fact, the lawsuits about the misappropriation of Gilles' properties continued for a century after his death and all of them were eventually restored to the Rais family.
Jean V had another reason to be doubtful that he could hang on to his ill-gotten gains. The contract for the sale of Champtocé was fiendishly complex and went through several drafts. The final agreement included the clause that Gilles could buy the castle back at any point within the next six years, at the price he had sold it for. Most commentators dismiss this as a motive: the money simply was not there. However, we know that the Duke had at least two spies in Gilles' household - Guillaume Grimaud and Guillaume Sauzaie - who were bribed to persuade their master to sell Champtocé (and, meanly, would not be paid unless they succeeded). It is certain that they would have told him that Prelati was claiming to be close to finding the Philosopher's Stone. If he could turn base metals into gold, money would cease to be a problem for Gilles.
This, then, is the financial aspect of the plot. As we see, it was not as simple as "follow the money", though it should be stressed that not one sou of the proceeds went to the Church; it was divided between the Duke's sons.
The politics, similarly, appears simple but is deeply complex, hinging as it does on the absurdity of a French war hero on trial in the quasi-independent duchy of Brittany. Charles VII owed his throne to two commanders, Gilles and Jehanne. He had singled them out from the rest by awarding them the highly unusual honour of a border of fleurs de lys around their coats of arms. If both had been executed for heresy, then it might be argued that he had won the crown with the help of the Devil. To smear Gilles was to smear Jehanne and, by extension, the French King.
Jean V's links with England were strong. Few writers explain exactly how strong they were. After his father died, his mother, Jeanne de Navarre, married the English king, Henry IV; her son, the future Jean V, became a ward of the Duke of Burgundy, one of the staunchest allies of the English. As Duke of Brittany, he operated a politique de bascule which was highly successful: between 1420 and 1427 he switched sides no fewer than five times. During Gilles' trial, he actually signed an important treaty with the English, so it is clear which way the pendulum was swinging at that time, and it was not in a direction favourable to the pre-eminent French commander standing before a Breton court
Besides, Jean V loathed the Lavals. A 17th century historian, François-Eudes de Mézeray, remarked that the Duke was “very glad to avenge his own offence in avenging that of God”. Michelet adds that he was all the more delighted to strike at the Lavals because the King had elevated the barony of Rais to a county and therefore Gilles from a baron to a count. The Duke had a paranoid fear that the Lavals were plotting against him; in December 1437, while he was negotiating with Gilles for the sale of Champtocé, he dismissed his cooks for fear of poison. Jean V would never have trusted Gilles completely; he was descended from the Lavals on his father's side and would have carried that name if it had not been for the complex deal that had eventually resulted in a passionately pro-French Laval owning a huge swathe of Brittany. All this must have rankled.
Gilles' judge Jean de Malestroit, usually described as the Bishop of Nantes, was also the Chancellor of Brittany. He was a lifelong supporter of the English, had led several embassies to London, and was strongly suspected of sabotaging the French cause - not least by Richemont, the Constable of France, who in 1426 kidnapped him and flung him into prison. Malestroit's chief aim in life was to maintain the independence of Brittany and prevent it from being subsumed into France, and he rightly supposed that an alliance with England was the best way to ensure this. Unlike the Duke, his allegiance never wavered.
The important fact to remember is that the French King had nothing to do with the trial of Gilles de Rais. It is impossible to make sense of what happened without understanding the separation between Brittany and France.
In the end it all came down to property and dirty politics.