A466 road about long and runs through the counties of Herefordshire and Gloucestershire in England, and Monmouthshire in Wales. It runs south from Kingsthorne, on the A49 south east of Hereford to Monmouth, crossing the A40. After crossing the River Wye at the Wye Bridge, Monmouth and Bigsweir Bridge near Llandogo, it follows a picturesque route south down the Wye valley through Tintern and Chepstow to the M48 motorway at junction 2. The road crosses the border between England and Wales at three places along its length: at Buckholt, Redbrook, and Bigsweir. It runs through an Area of Outstanding Natural Beauty, and
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