Relief for the Britons came when Cenwalh was exiled to East Anglia after a squabble with Penda of Mercia. Some time after his return he renewed the attack on the British tribes and in 658 his army met the Britons for a climactic battle at Peonnum. The Saxons were victorious, and Cenwalh advanced west through the Polden Hills to the River Parrett, annexing eastern and central Somerset. The territory gained was modest in size; Geoffrey Ashe suggests that Cenwalh's ultimate goal may have been gaining control over the valuable Glastonbury Abbey within it.