start adjacent to lay-by on a476 by carmel village sign. proceed north towards llandeilo to turn sharp left with extreme care (5.2 miles) onto b4300. proceed south on b4300, through llanarthne (10.5 miles) to turn left onto b4310 signposted national botanic gardens. climb hill past y polyn restaurant, through cefn abbey and descend to roundabout at national botanic garden entrance (16 miles). go straight on at roundabout (2nd exit) with care (roundabout is offset to left) to next roundabout where go straight on (2nd exit) to pass underneath a48 flyover (16.7 miles) and into villageof porthyryd where turn left (17 miles) on unclassified road signposted cefneithin. climb hill to village of cefneithin to finish by gateway approx 200 yards past cefneithin village sign (19.6 miles).