There is a direct reference to the hunt of the Twrch Trwyth in the catalogue of the marvels of the Island of Britain, which in some copies is appended to the "Historia Britonum" of Nennius preserved in the British Museum (Harleian MSS. 3859).
"Est aliud mirabile in regione quee dicitur Buelt. Est ibi cumulus lapidum, et unus lapis superpositus super congestum, cum vestigio canis in eo. Quando venatus est porcum Troynt, impressit Cabal, qui erat canis Arthuri militis, vestigium in lapide, et Arthur postea congregavit congestum lapidum sub lapide in quo erat vestigium canis sui, et vocatur Carn Cabal. Et veniunt homines et tollunt lapidem in manibus suis per spacium diei et noctis, et in crastino die invenitur super congestum suum."Lady Guest in her notes on the Mabinogion gives a description of the sites involved in the hunt for the Twrch Trwyth. The following is a modification of that description.
"There is another wonder in the region called Buelt. There is a heap of stones, and one stone laid on the heap having upon it the footmark of a dog. When he hunted the swine Troynt, Cabal, which was a dog of the warrior Arthur, impressed the stone with the print of his foot, and Arthur afterwards collected a heap of stones beneath the stone in which was the print of his dog's foot, and it is called Carn Cabal. And people come and take away the stone in their hands for the space of a day and a night, and on the next day it is found on its heap."
"Porth Cleis is listed as the site where the Twrch Trwyth landed, and commenced his devastating expedition through the Principality. The port is a small but well known harbour in Pembrokeshire, at the estuary of the river Alun. Although it is only capable of affording accommodation to what are now termed small craft, it was, in times past, a much frequented port, and was the landing-place in several marauding excursions of the Gwyddyl Ffichti, one of whom, named Boia, is recorded in the Liber Landavensis as having been the source of great annoyance to St. David and St. Telliaw. The former of these saints is traditionally reputed to have been a native of Porth Cleis, and to have been baptized at a holy well in its immediate vicinity.
"Mynyw, or St. David's, is the next place mentioned in the progress of the Twrch Trwyth, and then next to Aber deu Gleddyf, or Milford Haven. On leaving Aber deu Gleddyf, we find him overtaken by Arthur while destroying the herds of Kynwas Kwrr yVagyl, and this we may conjecture to have occurred at a place still called Kynwastori or Canaston, not far from Narberth. Blaengwaith Noe ab Arthur, near Lampeter Velfrey, and Buarth Arthur, and the Cromlech of Gwal y Filast, or Bwrdd Arthur (Arthur's Table), in the parish of Llanboipy, probably mark the course of this singular hunt to the Preselly Mountains, the highest range in Pembrokeshire. At the eastern extremity of these mountains rises the river Nyver, or Nevern, on the banks of which the British warriors drew themselves up in array, and close to the highest peak of the range, named Preselly Top, is the dingle of Cwm Kerwyn, where the Twrch Trwyth is said to have committed such dreadful havoc among Arthur's champions. Within a distance of two miles, Arthur's name is again perpetuated in the rugged summit of Carn Arthur, whence the imagination may easily trace some remembrance of the Twrch Trwvth and his progeny, in the names of the opposite eminence, Moel Dyrch; and of Tre Dyrcb, the adjacent farm.
"Leaving the Preselly Mountains, and passing through Aberteivi or Cardigan town, the Twrch Trwyth again appears in Dyffryn Llychwr, or Loughor, on the confines of Carmarthenshire and Glamorgan. The Dyffryn Amanw of the tale is identical with the valley of the river Amman, which falls into the Llychwr some few miles from the sea. In the Mvnydd Amanw we recognize the lofty heights, which form a natural boundary between the counties of Brecon and Carmarthen, called Mynydd Du, and Bannau Sir Gaer, or the Black Mountain and Carmarthenshire Vans. On this range tradition has assigned to Arthur a resting-place of the most ample dimensions, called Gwely Arthur, or Arthur's Bed, and near to the spot where the river Amman rises is an elevated knoll, called,Twyn y Moch, at the foot of which is Llwyn y Moch, both of which names may bear some allusion to the adventures detailed in the text. The same remark may be said to apply to the adjacent river Twrch, which rises on the Van, and runs into the Tawy, below Ystradgynlais. Another singular coincidence may be traced between the name of a brook in this neigbbourhood, called Echel, and the Echel Forddwyttwl, who is recorded in the tale as having been slain at this period of the chase. On the Llangadock side of the Black Mountain we meet with fresh reminiscences of the British monarch in Pen Arthur, and Coiten Arthur.
"The latter is one of two large rocks in the bed of the Sawdde river, said to have been the hero's quoit, which he flung from the summit of Pen Arthur to it's present position; a distance of about a mile. As there are several localities on the Tywi bearing the appellation of Dinas, it would be difficult to determine to which of them Din Tywi is intended to refer.
"At Ystrad Yw, we find ourselves once more on well-known ground, and hence we may conjecture that the course of the Twrch Trwyth lay across Carn Cavall and the Brecon Mountains to Abergwy, where the Wye falls into the Severn below Chepstow, and where the princely monster also dashes into the flood, to appear again but for a moment in Cornwall, before he vanishes entirely from our view."
