|Length:||14.9 miles (24 km)|
|Meets:||A483, B4568, B4390, B4385, A458, B4382, A495|
|Route outline (key)|
The B4389 is a south-to-north route crossing the Montgomeryshire hills west of the River Severn.
The route starts on the A483 500 m to the southeast of Aberbechan. From here it heads northwestward, crossing the Severn by means of Cilgwrgan Bridge, immediately followed by two further bridges across the no-longer navigable Montgomery Canal and Bechan Brook in the hamlet of Aberbechan itself. The road then continues along the Bechan valley, following the brook upstream.
After meeting the B4568 coming in from the left, the B4389 crosses the stream again and bends sharply right to follow the valley northward. The latter now becomes much narrower - and the road twistier - as it climbs to the village of Bettws Cedewain where the stream is crossed once more and the road bends sharply left and appears to run through the pub's beer garden.
The next village is Tregynon where the Bechan Brook is left. On the southern edge of the village the road TOTSOs right at a crossroads; the road to the left is a more direct route to Newtown. The road climbs to a summit before descending into the next valley. It crosses the River Rhiw at a narrow bridge (but no less narrow than some parts of the B4389 already) before following the river into New Mills. Here the road has to TOTSO left; the road ahead is the B4390 which continues along the Rhiw valley.
The B4389 climbs out of the valley, steeply in places, and continues across the hills. It eventually descends into Llanfair Caereinion, where it meets the B4385 at a T-junction by the church. Our road TOTSOs right and multiplexes along the B4385 for a short distance; that road has to TOTSO at the other end of the multiplex and the B4389 continues north to cross the River Banwy and reach a T-junction on the A458.
Originally this was the northern end of the B4389. However, the route was extended in the 1940s and now multiplexes east along the A458 for a couple of miles downstream. It turns left and regains its number at Heniarth, where the A458 turns sharply right. The B4389 then continues north along what used to be the A495 (and originally B4394). It crosses the hills, cutting off meanders of the River Banwy, before descending once again into the river valley and ending on the current route of the A495 close to the site of Mathrafal Castle, 1 km to the southwest of Newbridge (over the River Vyrnwy).