This walk approaches the 'big three' summits of the Brecon Beacons (Corn Du, Pen y Fan and Cribyn) from the north, using one of the most attractive of the various ascents to the main northern escarpment. But instead of heading directly over the summits, it continues south along an impressive ridge and down to the Lower Neuadd Reservoir. This leaves a good deal of uphill work again for the latter part of the walk, but by bagging Cribyn, Pen y Fan and Corn Du late in the day, you should find them a lot quieter – if not have them entirely to yourself! In fine weather the views throughout are splendid.
[1] From the parking area (SO006244), follow the delightful track beside the Nant Cwm Llwch brook. At Cwm Llwch farmhouse, take the waymarked path to the right that bypasses the track. Further on, cross a stile and continue up the steep grassy slopes (another path stays lower and goes to Llyn Cwm Llwch). The path curves round the hillside above Llyn Cwm Llwch, Corn Du and Pen y Fan above – a fine sight. (A path up from the lake joins from the left. Remember to keep to the higher, left-hand path on your descent later). You reach the skyline near the memorial to Tommy Jones, a child who lost his way and died of exposure here. Continue climbing up towards Corn Du. You can either go to its very top, where you turn right (south), or bypass it and bear right.
[2] Heading south you are soon at Bwlch Duwynt. Keep ahead on the eroded path along the edge of the escarpment over Craig Gwaun Taf and Graig Fan Ddu.
[3] At a large cairn, turn left down a narrow gully which descends the escarpment quite steeply. This loose, stony pink path isn’t very pleasant; it doesn’t last long but requires some care. Continue down the grassy hillside (which may be a bit boggy in places) towards the right and dam-end of Lower Neuadd Reservoir (which may not be marked on the Landranger map).
[4] Go through a gate and cross the top of the dam. Then cross a footbridge and go up to the reservoir access road. Turn left and follow it for a short distance, soon turning right along a track and then left through a gate up another track. Bear left along the broad, stony track – an old Roman road - that climbs steadily to what is known as The Gap, the pass between Fan y Big and Cribyn.
[5] If you’ve got the energy, turn left and climb the steep path to the top of impressive, pyramid-like Cribyn (795m/2,608ft), less tramped than its neighbours. There’s a corresponding descent the other side.
Alternatively, you can follow the Beacons Way route which skirts it to the south.
Whichever you choose, continue along the path at the edge of the escarpment up to the 886m/2,907ft flat rocky summit of Pen y Fan, the highest point in Britain south of Snowdonia. A gentler descent and ascent leads onto the flat top of Corn Du (873m/2,863ft). From here retrace your initial steps back to the start.