I went off piste, big time.
Just below Moelfre"s right hand corner, where the old road from Cors Y Gedol comes up from the coast, you take small gate on your left, as the road turns off around the bend.
From the Cors y Gedol upper road, you will notice three distinctive Scots Pine trees, off to your immediate left, about a mile distant, a clear indication that the ruined dwelling underneath was frequented by Drovers in the past.
I made for those, trying to avoid quite a few cows, and a large Bull, in the process.
On reaching the Scots Pines, continued up the mountain side, until i met the road from lower Dyffryn to Cwm Bychan.
The entire mountain of Moelfre was now on my right, so after a bit of off the beaten track, ever so boggy and wet but hellish enjoyable navigation, i eventually came to the other side of the mountain, with llether right in front of me at he top of the valley.
None of the navigation was difficult, but going totally off the beaten track, was part of the enjoyment of the whole Bank holiday, and i knew where my eventual target of llether was located, i just walked until it came into view.
I was half expecting to find one or two skeletons of lone walkers, who had come to grief, and because of the extreme solitude of the Rhinogs, had cried for assistance, but fallen on death ears.
I was certainly in the wilds of the Dyffryn mountains, as there were no worn paths anywhere in sight, just me and the barren mountains.
Eventually coming to the famous wall, i then followed it all the way up to llethers summit, and then had a look at where i went wrong the other day.
The weather by early afternoon had turned out really nice, with the early morning mist having now burnt off.
Thankfully none of the terrain, was technically difficult, just exploring a part of the Rhinogs, where there are no designated paths on the OL18 map.
In total, the walk lasted only four and a half hours, and if one is daft enough to go exploring very remote locations, by ones self, it comes highly recommended.
Coming to grief, thankfully never came to mind, just exploring nature at its finest, me against the elements, and living to tell all about my Bank holiday adventure.
I am not quite sure about Shirely Toulsons lack of accuracy, because the direction of the Harlech to London Coach road, is never in doubt.
From llanbeder, it turned up towards Cwm Nantcol, to the left of the Victoria pub, and then approached the Rhinogs from the Cwm Bychan direction, exactly where, i do not know, but it certainly came this way.
The Scots Pines i talked about, are a known indicator of Drover activity, as their such a rarity in this part of North Wales, there some others further down the road just past Pont Fadog, in the Bwlch Y Rhiwgyr direction, so i recon the ruined building must have been an inn or rest spot for the Drovers coming up from the coast.
Those Scots Pines look straight towards Cors Y Gedol Hall, and eventually Lletty Loeger and Pont Fadog, so the coach road and route taken by the Drovers, was in this area, but i certainly agree with your that Toulsons book, may be inaccurate in some respects.
Walking towards those Pine trees, i could see a very poorly defined trackway, now obscured by grass, but there's no doubt the Drovers came this way.