wall of his cell and then escaping onto the roof, before using rope ladders provided by an accomplice to get down to the River Thames, across the river and then on eventually to safety in France. Victorian writers suggested that, given later events, Isabella might have helped Mortimer escape and some historians continue to argue that their relationship had already begun at this point, although most believe that there is no hard evidence for their having had a substantial relationship before meeting in Paris. Isabella was reintroduced to Mortimer in Paris by her cousin, Joan, Countess of Hainault, who appears to have approached Isabella suggesting a marital alliance between their two families, marrying Prince Edward to Joan's daughter, Philippa. Mortimer and Isabella may have begun a physical relationship from December 1325 onwards. If so both Isabella and Mortimer were taking a huge risk in doing so—female infidelity was a very serious offence in medieval Europe, as shown during the Tour de Nesle Affair—both Isabella's former French sisters-in-law had died by 1326 as a result of their imprisonment for exactly this offence, and their alleged lovers had been brutally executed. Isabella's motivation has been the subject of discussion by historians; some believe 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. One historian has described their relationship as one of the "great romances of the Middle Ages" in spite of the fact that they are reputed to have murdered her husband. They also shared a common enemy—the regime of Edward II and the Despensers. Taking Prince Edward with them, Isabella and Mortimer left the French court in summer 1326 and travelled north to William I, Count of Hainaut. As Joan had suggested the previous year, Isabella betrothed Prince Edward to Philippa of Hainault, the daughter of the Count, in exchange for a substantial dowry. She then used this money plus an earlier loan from Charles to raise a mercenary army, scouring Brabant for men, which were added to a small force of Hainaut troops. William also provided eight men-of-war ships and various smaller vessels as part of the marriage arrangements. Although Edward was now fearing an invasion, secrecy remained key, and Isabella convinced William to detain envoys from Edward. Isabella also appears to have made a secret agreement with the Scots