Edward's opponents began to gather around Isabella and Mortimer in Paris, and Edward became increasingly anxious about the possibility that Mortimer might invade England. Isabella and Mortimer turned to William I, Count of Hainaut, and proposed a marriage between Prince Edward and William's daughter, Philippa. In return for the advantageous alliance with the English heir to the throne, and a sizeable dower for the bride, William offered 132 transport vessels and 8 warships to assist in the invasion of England. Prince Edward and Philippa were betrothed on 27 August, and Isabella and Mortimer prepared for their campaign.