In 652 Cenwalh was fighting at Bradford on Avon. Who he was fighting against is not entirely clear. But the Welsh were there led by Morgan Mwyfawr. At least one chronicle calls it a civil war implying he was also fighting other West Saxons. In 658 he defeated the British at Penselwood. He defeated them a second time at Postbury. By 661 he had regained control over Somerset. But Mercia was constantly pushing into his territory. It was also in 661 that Wulfhere of Mercia controlled all lands north of the Thames including the abbey at Dorchester. This was one reason Cenwalh created the new diocese at Winchester which was further away from Mercian control. Cenwalh's territory in the mid-660s was significantly reduced by the Mercians. Cenwalh died in 672. After his death his widow, Queen Seaxburh, did what she could to hold Wessex together.