Visited 10th December 2002: The weather was bitterly cold. I had a pleasant stroll up through the Nant yr Arian forestry before realising I wasn't on the right footpath at all (thanks to my old OS map which didn't have the upper lake marked on it). I had to cut across country to correct my mistake.
The footpath I should have been on starts at the Llwernog Trout Farm entrance east of the Nant yr Arian Forestry Cenre (SN72458130). It's really a bridlepath, following a farmer's track from the A44, past the Trout Farm buildings, and across the earthen dam that forms the lower of the two lakes. The track briefly heads northwest before hooking to the northeast and up onto Blaen Llwernog (the hill that the stones get their name from).
The footpath was easy to follow while there were faint ruts along it, but when it passed to the west of Blaen Llwernog's summit the ruts petered out. I guessed my way from there, heading northwest. A forestry plantation came into sight, then I spotted an elegant little Mam hill outlined against the trees. I had a feeling this was the direction to head in, and sure enough I ended up at a gate in the corner of the field. Here the footpath crosses the boundary fence. On the other side of the gate, before the forestry plantation, are the stones. They sit to the right of the footpath on slightly elevated piece of ground.
Perhaps I should have started this essay by saying, these two stones are not very big. It's a long walk to see stones as tiny as these, so if you want something megalithic rather than minilithic, don't come here. Fortunately I already knew this before I started out, and I was really pleased to find the site. The walk up was cold and windy, but exceptionally beautiful, and the surrounding hills looked fantastic. At the stones the forestry spoils the views towards Pumlumon Fawr, which I suspect were an important element to whoever erected them. On the bright side, the trees formed an excellent windbreak, so I stopped to have lunch leaning against a stock fence before heading back to the car.
According to Cambria Archaeology records (sadly no longer online as far as can tell) the Blaen Llwernog stones are either the remains of a round barrow, or simply a small stone pair. In either case they probably date back to the Bronze Age.