Hay-on-Wye in Hay is a sub-office of Hereford, and therefore although in Wales has an English postal address, being part of the HR3 postcode. Hay-on-Wye is a Welsh community with a Town Council. Its boundary follows the English border/Dulas Brook from the River Wye southeastwards for just over a kilometre, turns south-west to a point just south of Oakfield house, thence north to Greenpit Farm and north westwards, enclosing the Hay Showground and meeting the National Park boundary near the B4350, Brecon Road. From this point, it follows the National Park boundary to the River Wye and the river back to
England–Wales border then runs westwards to the River Teme, and follows the river southeastwards through Knighton before turning south towards the River Lugg at Presteigne, which is within Wales. The boundary continues southwards across hills to the River Wye, and follows the river upstream for a short distance to Hay-on-Wye, on the Welsh side of the border. It continues southwards and rises through and across the Black Mountains, following the Hatterall Ridge past Llanthony on the Welsh side and Longtown on the English side, to reach the River Monnow near Pandy. It then generally follows the river, past Pontrilas (in England) and