Just another GR refugee. Other than that, I had a stroke in 2004, and read almost anything I can get my hands on, though I have a particular weakness for history, mystery, and historical fiction.
Chapter 3 of Trial by Battle takes us through the French territory at the heart of the animosity between the English and French crowns: Gascony. The king of England was also Duke of Aquitaine (thanks to Eleanor of Aquitaine), and as such owed homage to the king of France. This was always a difficult situation - in part because one king owing homage to another was an idea the feudal system didn't deal with very well, and also because the Gascon lords didn't want to be ruled by anyone at all.
The Gascons found that being ruled from afar, by a duke who remained mostly in England, was superior to having dukes at home to prevent them from doing anything they liked. And if they couldn't get their way from the English king; well, they could always ask for their pleas to be heard at the Parlement of Paris. (The Parlement of Paris was not a political or governing parliament like the English Parliament, but a judicial body.) They could play the English and French crowns against each other, in order to get their own way.
A strong king, like Edward I, had managed his ducal holdings through a shrewd mixture of of diplomacy, bribery, bullying, and knowing when enough was enough, and that it was time to back off. His son, Edward II, was a weak king, and the Gascon lords mostly got the better of him. He was not helped by generally sending a new senechal there every year; whether they were competent or otherwise, none of them would have enough time there to become experts in the local situation. More and more holdings slipped into the power of the French crown, and Edward II seemed completely unable to stop this process.
It all culminated in a war the English didn't want in the 1320s, in which they were steam-rollered by the French, and the French strongly suggested that the only English ambassador who would make much ground in negotiating peace with them was Edward's "evil" out-of-favor wife, Queen Isabella (the only sister of their king, Charles IV). Oh yes, and English nobles fed up with their weak and indecisive king, the Despensers who had given him poor advice, and the resulting humiliation at the hands of the French.