[2][3] Roger Mortimer of Wigmore was a powerful Marcher lord, married to the wealthy heiress Joan de Geneville, and the father of twelve children.

[9] Isabella's motivation has been the subject of discussion by historians; most agree that there was a strong sexual attraction between the two, that they shared an interest in the Arthurian legends and that they both enjoyed fine art and high living.

[12] Mortimer's supporters in England started to send him victuals, armour and other aid by March 1326,[13] which Edward tried to stop, and also ordered his ports to be on the lookout for spies entering the kingdom.

Without French support, Isabella and Mortimer left Paris in the summer of 1326, taking Prince Edward with them, and travelled north-east into Holy Roman Empire territory to William I, Count of Hainaut.

[12][15] As Joan had suggested the previous year, Isabella betrothed Prince Edward to Philippa, the daughter of the Count, in exchange for a substantial dowry[16] She then used this money to raise a mercenary army, scouring Brabant for men, which were added to a small force of Hainaut troops.

Isabella struck west again, reaching Oxford on 2 October where she was "greeted as a saviour"—Adam Orleton, the bishop of Hereford, emerged from hiding to give a lecture to the university on the evils of the Despensers.

Isabella responded by marching swiftly west herself in an attempt to cut him off, reaching Gloucester a week after Edward, who slipped across the border into Wales the same day.

By now desperate and increasingly deserted by their court, Edward and Hugh Despenser the Younger attempted to sail to Lundy, a small island just off the Devon coast, but the weather was against them and after several days they were forced to land back in Wales.

[24] With Bristol secure, Isabella moved her base of operations up to the border town of Hereford, from where she ordered Henry of Lancaster to locate and arrest her husband.

[25] After a fortnight of evading Isabella's forces in South Wales, Edward and Hugh were finally caught and arrested near Llantrisant on 16 November, which brought an end to the insurrection and the civil war.