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 an exclave of Flintshire, between Bangor-on-Dee (in Wales) and Whitchurch (in England). Returning to the River Dee as far as Chirk, the boundary then loops to the west, following Offa's Dyke itself for about , and including within England the town of Oswestry, before reaching the River Vyrnwy at Llanymynech. It follows the Vyrnwy to its confluence with the River Severn, and then continues southwards, rising over Long Mountain east of Welshpool. East of Montgomery, the boundary again follows the line of Offa's Dyke for about , before looping eastwards to include within Wales a large area near Churchstoke. It