England–Wales border point. In 926, Edward's successor Athelstan, "King of the English", summoned the Welsh kings including Hywel Dda of Deheubarth to a meeting at Hereford, and according to William of Malmesbury laid down the boundary between England and Wales, particularly the disputed southern stretch where he specified that the eastern bank of the Wye should form the boundary. By the mid-eleventh century, most of Wales had become united under the king of Gwynedd, Gruffudd ap Llywelyn. In 1055, he marched on Hereford and sacked the city. He also seized Morgannwg and the Kingdom of Gwent, together with substantial territories east of
England–Wales border Shrewsbury, and Hugh d'Avranches at Chester, creating a new expansionist earldom in each case. In the Domesday Book of 1086, Norman lands are recorded west of the Wye at Chepstow and Caldicot in the Gwent Levels (); over the whole of north east Wales as far west as the River Clwyd, an area known to the Welsh as the "Perfeddwlad"; and west of Offa's Dyke, especially in Powys where a new castle was named, after its lord, Montgomery. Domesday Book no doubt records the extent of English penetration into Wales. This suggests that Offa's Dyke still approximately represented the boundary