A midday start allowed the early low cloud to clear and we set off in warm sunshine on the familiar route NW out of Rhayader via the lane to Dderw Bridge and the RUPP track that ascends easily to the 463m summit of Esgair Dderw, a grassy top that has a single standing stone named Maen-serth. The views were much clearer than last time and the cooling breeze was welcome as we sat for a bite to eat. The red kites had appeared as usual on the approach, much to the consternation of the rooks in the woodland of Cwm-bach who react defensively to the threatening presence of any raptors.

The track marches on along the southern flanks of Penrhiw-wen to join the minor road to Pont ar Elan, and just beyond the head of the Nant Lwyd we left the road on a thin path that slants down the hillside directly to the bridge. A clear prospect over the northern end of Craig Goch reservoir made a change from our previous dull grey views and a few day trippers were lazing on the banks of the Afon Elan.

A short way up the road a sign indicates the start of the long track that runs for over 6 miles (10km) to the western end of Claerwen. In these rolling hills the angles are easy and the miles can be swift, and we ended the first day at the summit of Carn Ricet, finding a good patch in the typical tussocky grass near a small water tank and pole, maybe a type of rain gauge.

The indefatigable skylarks were singing full throttle from all directions at dawn and we opened the door to a clear blue sky, although the hills to the north were still capped in early cloud as we resumed our route south-westwards.

The track briefly becomes rather wet and multi-stranded further on and a few forlorn marker posts lie collapsed on the ground, but the going is easy and it soon swings around the head of the Nant Cormwg to Blaen Rhestr and the hut above the Cerrigllwydion Lakes. To the south is a view of the broad catchment plain of the Nant Bryn and Ffos Gyrnant which eventually drain into Claerwen.

We made a detour to the tussocky shore of the upper lake and ascended the rocky outcrops of Blaen Rhestr for a more elevated view.

We left the RUPP for an easy walk over Esgair Cywion and down to the Claerwen reservoir track that terminates at the farm a short way west, a very remote dwelling with an assortment of horses and donkeys who eyed us warily until we departed across the bridge to join the bridleway westwards. There is now a footbridge over the incoming streams of the Afon Claerddu at SN817671.

The bridleway is very wet here but our course was directly uphill on easy dry ground to the 496m rise of Esgair Wen where the rain gauge shown on the map is still there in the tussocky grass, a sorry looking cylinder surrounding by a square of old fence posts.

Llyn Gynon is in view far to the south, but a direct line would traverse a huge badass bog. We headed initially westwards to Bwlch yr Hendre and spied a strategy to avoid the boggy badlands: by traversing around the bases of the intervening hillocks of Bryniau Pica, using sheep tracks where available, we found easy and mainly dry walking around the headwaters of the Nant Gwinau. Looking across the broad wet plain, this spot exudes a strong sense of remoteness.

Approaching Llyn Gynon the terrain generally has a greater proportion of wetter and much rougher bits, and as is often the case in these hills, the remote lakes have very tussocky pathless shores. We arrived at the northern tip and slowly lurched our way around the often boggy matted tussocks of the western shore, and although the lake is a marvellous sight and the highlight of the trip, we constantly felt we were earning it.

From this intimate acquaintance the lake seemed much grander than our foreshortened view from the bridleway on our last visit to this region, and the wavelets breaking on the shore in the stiff breeze added to the impression.

We picked up the bridleway running eastwards from the south of the lake along the base of Crug Gynon, vague and wet at times, and a drier path has been forged a little up the slope to avoid some boggy bits. The line crosses the Nant y Ffin and Nant yr Helyg to swing left around the lower flank of Esgair Garthen, another good vantage point to appreciate the extensive boggy wilderness stretching back to Llyn Gynon.

The bridleway ascends the few contours to the plateau of Esgair Garthen by a tiny stream not shown on the map (there is an alternative track traversing the 480m ring contour that rejoins it at SN822641). Here we left the bridleway on a side track that traverses the long broad expanse of the hill on the highest ground where Claerwen eventually comes into view, and we made a good final pitch in the middle of the ridge.

The dawn brought another excellent clear morning for an easy walk eastwards along the broad top, swinging NE around an extensive boggy depression to the top of the northern slopes above the blue waters of Claerwen and descending to the dam.

A short walk down the road is the signed bridleway that ascends to the mast and enclosure on Cefn Llanerchi and descends through the forest to the bridge between Garreg-ddu and Caban-coch reservoirs. Across the bridge is the start of a cycle track below the road that hugs the lake, an easy pleasant walk northwards with the colourful heathery cliffs of Mynydd Dolfolau looking impressive ahead.

We left the cycle track via a gate onto the road a short way before the start of the bridleway that climbs steeply eastwards near the Nant Dolfolau, a very good path that emerges onto the saddle in the hills near some old workings. Forking L at the junction, the path soon approaches a broad boggy expanse of reeds at the head of the Nant Madog:- before the reedy area, a grassy path branches off R that cuts off the boggy section and joins the stream a bit lower down. The path leads down directly to the road head and we took the narrow lane to the B4518.

From the B road the dismantled railway route makes a pleasant return to Rhayader. This passes over the old Rhayader tunnel which has an information board showing the species of bats recorded there, and various other notes.