Take the A40 out of Abergavenny towards Brecon.
Next, take a right at the roundabout on the outskirts of Brecon and travel up the A470/A438 to Bronllys, Glasbury, Clyro, Whitney on Wye, Staunton on Wye.
Turn right off the A438 at Bridge Sollers over river Wye (stop on the bridge and take in the view, especially early or late on a sunny day).
Follow the small lanes carefully down to Madley. It is simpler to take a left turn onto the B4532 at Madley towards Clehonger/Hereford.
Turn right on to A465 at the give way junction and back to Abergavenny.
If you want to explore the back lanes some more, take a right instead at Madley on the B4532 towards Hay on Wye and cut through the small lanes to come out on the A465 closer to Abergavenny at Pontrilas or Pandy. But watch out for grass growing up the middle of the road on some of these back lanes!
Beautiful countryside throughout.