Even more recently Ixer and Bevins have proved that the Altar Stone could not possibly have originated in the Cosheston Beds as H H Thomas proposed almost a hundred years ago, thus removing any scientific basis for the sea route. They have concluded that instead the Altar Stone comes from the eastern limit of the Senni formation. And I would point out that the Boar's route passes down the Ystrat Yw valley which is at the eastern limit of the Senni Formation. Once more demonstrating the Boars uncanny knack of passing through all the known origin quarries for the bluestones of Stonehenge.
It should also be noted that pigs feature mightily in the archaeology of Durrington Walls, the 'township' which housed the workers who erected Stonehenge. Recent results show that 90% of the meat consumed there were pigs and that many of these 'little piglets', (scientific study has shown, from teeth analysis) were herded to Durrington Walls from West Wales.
What we could have here is a bona fida 5,000 year old record of one of the most enduring mysteries in world history, to use a few hackneyed phrases, hidden in plain sight, beneath our very noses. In the Hunt of the Twrch Trwyth we may have a precisely mapped out route of the Bluestones across the neolithic Welsh landscape.
Now when Arthur approached, Twrch Trwyth went on as far as Preseleu, and Arthur and his hosts followed him thither, and Arthur sent men to hunt him; Eli and Trachmyr, leading Drutwyn the whelp of Greid the son of Eri, and Gwarthegyd the son of Kaw, in another quarter, with the two dogs of Glythmyr Ledewig, and Bedwyr leading Cavall, Arthur's own dog. And all the warriors ranged themselves around the Nyver.
I am not the first to notice that this outcrop of rhyolite known as Craig Rhos-y-felin has the appearance of a sleeping boar with its bristly back and it's snout to the ground. Perhaps the author imagined the giant boar resting at this site. Anthropologist Mary-Ann Ochota has likened the dramatic outcrop to 'a sleeping dragon or the scales of a mythical beast'. It is now certain that this neolithic quarry provided at least one of the Stonehenge bluestones. Neither can there be any doubt that this part of the route of the Twrch Trwyth is that which is specified in Culhwch.
And there Twrch Trwyth made a stand, and slew four of Arthur's champions, Gwarthegyd the son of Kaw, and Tarawc of Allt Clwyd, and Rheidwn the son of Eli Atver, and Iscovan Hael. And after he had slain these men, he made a second stand in the same place. And there he slew Gwydre the son of Arthur, and Garselit Wyddel, and Glew the son of Ysgawd, and Iscawyn the son of Panon; and there he himself was wounded.
It has occurred to others as well as to me that the missing stones of Waun Mawr fall short of the numbers required to make up the 84 stones which eventually arrived at Stonehenge. That the people who moved the Welsh stones picked up the Alter stone on their way to Salisbury Plain, might suggest that other stones along the route may have found there way there also. Moreover, I wouldn't be surprised if at least one of the stones has an Irish origin. Both Geoffrey's account of Merlin's acquisition of the Giants Dance and the Hunt for the Twrch Trwyth begin in Ireland, possibly the same part of Ireland.