A former kingdom of central England. It was established by invading Angles in the 6th century ad in the border areas between the new Anglo-Saxon settlements in the east and the Celtic regions in the west. Becoming dominant in the 8th century under Offa, it expanded to cover an area stretching from the Humber to the south coast. Its decline began after Offa’s death in 796 and in 926, when Athelstan became king of all England, it finally lost its separate identity. In modern times the name has been revived, for example, in the ‘West Mercia Authority’, an area of police administration covering the counties of Hereford and Worcester, and Shropshire.