During the early Anglo-Saxon period the area of the modern city lay across a frontier separating two peoples. Birmingham itself and the parishes in the centre and north of the area were probably colonised by the "Tomsaete" or "Tame-dwellers", who were Anglian tribes who migrated along the valleys of the Trent and the Tame from the Humber Estuary and later formed the kingdom of Mercia. Parishes in the south of the current city such as Northfield and King's Norton were colonised during a later period by the Hwicce, a Saxon tribe whose migration north through the valleys of the Severn and Avon followed the West Saxons' victory over the Britons at the Battle of Dyrham in 577. The exact boundary between the two groups may not have been precisely defined, but is likely to be indicated by the boundaries of the later dioceses of Lichfield and Worcester established after the 7th century conversion of Mercia to Christianity.