These attacks marked the beginning of sustained pressure from the expanding kingdom of Mercia. In time this would deprive Wessex of its territories north of the Thames and the (Bristol) Avon, encouraging the kingdom's reorientation southwards. Cenwealh married Penda's daughter, and when he repudiated her, Penda again invaded and drove him into exile for some time, perhaps three years. The dates are uncertain but it was probably in the late 640s or early 650s. He spent his exile in East Anglia, and was converted to Christianity there. After his return, Cenwealh faced further attacks from Penda's successor Wulfhere, but was able to expand West Saxon territory in Somerset at the expense of the Britons. He established a second bishopric at Winchester, while the one at Dorchester was soon abandoned as Mercian power pushed southwards.