After the Romans left Britain in AD 407, the country was raided by Picts from Scotland, Angles and Saxons from Germany and Jutes from Denmark. Within 200 years most of England was under Anglo-Saxon rule, divided into seven Kingdoms: Kent (mostly Jutes), Essex, Sussex, Wessex, East Anglia, Mercia and Northumbria. As a guide, Wessex consisted of Hants, Dorset, Devon, Somerset and Wiltshire. Mercia's boundaries varied a great deal but could be said to lie between the Thames and Humber. The capital of Wessex was Winchester and important towns in Mercia were Lichfield, Repton and Tamworth. King Offa of Mercia was a powerful king of this period and built the dyke along the English/Welsh border. Although nominally King of England, really he was only accepted South of the Humber. He won a resounding victory over the Norsemen and Cornish at Hingston Down near Callington in Cornwall in 836 and also conquered Mercia in 829 but lost it again in 838. He paved the way for national political unification which was achieved by King Athelstan in the 10th century. Although Egbert was King, the remaining kingdoms retained sub-kings or Ealdormen.
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