1422: Charles VI of France dies leaving the throne of France to his recently enforced heir Henry V of England, who is soon crowned Henry II of France. Within a few years the Dauphin has been captured and joined the Dukes of Orleans and Angloueme in prison. The Duke of Burgundy is greatly rewarded for his aid, and the Valois-Angevins are too busy in Naples to do anything more than consolidate in Provence. Most of the other duchies slip into independence.
15 years later Henry V and II dies, leaving the throne to his teenaged son, Henry VI and III, though his brothers Edward and John gain the Duchies of Aquitane and Toulouse which have been seperated from the main lands around Paris due to the need for closer supervision to prevent rebellion. Henry VI has inherited more than a crown from his maternal grandfather though, and after a bout of insanity in 1452, is declared incapable. Edward, Duke of Aquitane takes up the regency after a brief power struggle with the younger, but arguably more capable, John of Toulouse. In the meantime the lords of Aqutiane begin to assert more independnece with their Duke in London. Henry's son Edward will is crowned Edward IV and I in 1475 after his father's forced abdication, while Aquitane passes on soon afterwards, leaving behind an heir every bit as mad as the late King. Quite without intention the Duchies of Aqutiane and Toulouse are now every bit as independent as the other French duchies, and with several weak kings in succssion, the Duke of York seeks to assert his claims to the thrones on the death of Edward IV/I and accession of his underage son Henry VII/IV under the regency of the Duke of Toulouse. Gathering support in England, he is able to sweep south and take London, crowning himself Edward V/II, but Henry retains control of the Royal Demense around Paris for now, though his title of 'King of France' is rapidly becoming as nominal as that of the Holy Roman Emperor next door.
And here's a somewhat different map from my usual style.