Penda of Mercia
According to the "Flores Historiarum", attributed incorrectly to Matthew of Westminster, the Britons were still in possession of Exeter in 632, when it was bravely defended against Penda of Mercia until relieved by Cadwallon, who engaged and, according to Geoffrey of Monmouth, defeated the Mercians with "great slaughter to their troops". However, since the late 19th century this siege has not been considered a historical fact.