Hay-on-Wye the north-easternmost tip of the Brecon Beacons National Park, just north of the Black Mountains. The town is just on the Welsh side of the border with Herefordshire, England, here defined by the Dulas Brook. Where the brook joins the River Wye just north of the town, the border continues northwards along the river. The Wye was the boundary between the former counties and districts of Radnorshire and Brecknockshire. The adjacent village of Cusop lies on the English side of the Dulas Brook. The nearest city is Hereford, county town of Herefordshire, some to the east. The Royal Mail depot
England–Wales border their areas formed into new counties, or amalgamated into existing ones. At this point, the boundary between England and Wales, which has existed ever since, was effectively fixed. In the border areas, five new counties were created – Denbighshire, Montgomeryshire, Radnorshire, Brecknockshire and Monmouthshire – and Flintshire gained some additional territory. However, several of the marcher lordships were incorporated in whole or in part into English counties. The lordships of Ludlow, Clun, Caus and part of Montgomery were incorporated into Shropshire; and Wigmore, Huntington, Clifford and most of Ewyas were included in Herefordshire. According to John Davies: Thus was created