England
Queen Isabella
The whole sad story illustrates how powerful were the earls of England, and how royal favor badly handled could lead the kingdom into chaos and civil war. The constitutional issues could be glossed over because Edward III was Edward II's own son and so was the legitimate heir anyway. Technically, Edward II abdicated in favor of his son, but this was done under threat of force. He was most likely murdered while in prison. Since there was no change in dynasty, the rebels could pose as defenders of the realm.
Thomas of Lancaster's son, Henry, was restored to his estates and was made head of a regency council (Edward III was still a boy). In reality, Isabella and Roger Mortimer ruled England. When some of the great lords rebelled in 1330, Isabella and Mortimer were defeated and one of Edward's uncles was executed.
Edward III was still only a teenager, but he acted swiftly in this crisis. He surprised Isabella and Mortimer at Nottingham Castle. Roger was taken straight to London where he was tried by Parliament and executed. Isabella was devastated, as she truly loved him.
Edward III had been crowned in 1327, but it was only now, in 1330, that he took power into his own hands. Edward III was the opposite of his father. He worked closely with the barons and kept them near the reins of power. He had loyal friends, but no one whom he favored to the neglect of others (at least not until he was an old man). And, most importantly, he was successful in war.