In Christmas 1325 she was still at her brother's court and encountered Roger Mortimer. Mortimer, 3rd Baron Mortimer of Wigmore and 1st Earl of March, had fled England after escaping from the Tower of London where he had been imprisoned for life after rebelling against Edward in the Despenser War. Rumors that Isabella and Mortimer developed a romantic relationship led them to leave the royal court. Each of them was married; Mortimer had gained great wealth and land through his wife.
According to the contemporary biographer who wrote the Vita Edwardi Secundi ("Life of Edward II"), Mortimer threatened to slit Isabella's throat if she returned to Edward. They first went to Flanders, then Isabella went to Ponthieu to raise troops and Mortimer (with Prince Edward) went to raise support in Hainault.
On 24 September 1326, Isabella and her son arrived back in England (see illustration). London allied with her, and Edward II fled westward, hiding out in Wales for a few weeks until he was captured on 16 November and imprisoned in Kenilworth Castle. A January 1327 Parliament was convened to discuss the situation, but they had a problem: there was no mechanism for removing a king. A delegation was sent to inform him that if he did not abdicate in favor of his son, his son might be disinherited and the kingship go to an alternate candidate. Edward chose to abdicate on 21 January. Edward II was crowned on 1 February.
In truth, the next few years in England were run by Isabella and Mortimer as regents for the young Edward. Their rule was not welcome by many of the barons, and the threat of civil war was never far away. Also, there were many lawyers and others who claimed Edward II was still king, and the chance that former supporters would try to restore him was not zero. Edward II was moved from Kenilworth to the more secure Berkeley Castle and put under the charge of Lord Berkeley. On 23 September, a message came from Berkeley that Edward had died from a "fatal accident." Rumors abounded: that Isabella had him killed; that Mortimer had him killed; that he had escaped and was hiding in disguise somewhere in Wales or on the continent. Edward's heart was given in a silver casket to Isabella.
When Edward III came into his majority, Isabella's authority in the country faded, although as the king's mother she was treated well. Edward had Mortimer taken to the Tower, after which he was accused of assuming royal power improperly and other crimes. On 29 November 1330, he was taken from the Tower to Tyburn Hill and hanged. His wife was pardoned of any part in her husband's crimes, and all Mortimer's lands were taken by Edward.
Isabella wound up in Castle Rising in Norfolk with a yearly income of £3000, which rose to £4000 by 1337. Her lifestyle was lavish with plenty of staff and extras like minstrels. The She-Wolf who had turned on her husband and taken over a country doted on her children and grandchildren and became more interested in religion, making several visits to shrines. She eventually took the veil with the Poor Clares. When she died on 22 August 1358, she was buried at the Franciscan church at Newgate with the silver casket containing Edward's heart.
She survived the accusations of an improper relationship with Mortimer, but she knew well the dangers involved in female infidelity. In fact, she herself was intimately involved in a French royal scandal involving adultery. Tomorrow I'll tell you about the Tour de Nesle affair.