Powys as the easternmost of the major kingdoms of Wales came under the most pressure from the English in Cheshire, Shropshire and Herefordshire. This kingdom originally extended east into areas now in England, and its ancient capital, Pengwern, has been variously identified as modern Shrewsbury or a site north of Baschurch. These areas were lost to the kingdom of Mercia. The construction of the earthwork known as Offa's Dyke (usually attributed to Offa, King of Mercia in the 8th century) may have marked an agreed border.