 The same year Madog was able to rebuild Oswestry Castle, a fortress of William Fitzalan.It would seem likely that he had gained both the fortresses of Oswestry and Whittington in 1146.At this time the King of Gwynedd, between 1149 and 1150, Owain Gwynedd was exerting pressure on the borders of Powys, despite the fact that Madog was married to Susanna, Owain's sister.