Following on from the Myrddin stanza 17 in Pen. 98, see Myrddin Emrys, we have:
“Vch law rhyd y garw faen ryde
y mae bedd Rhun ap Alun Dyv[ed]”
In the version of made from the manuscript in Widow Wynn’s possession this takes the form:
“ychlaw rhŷd garwvayn ryde
y may bêdh Hun ap Alim Dyfe.”
“Above the ford of the rough stone
is the grave of Rhun son of Alun Dyfed.”
Pen. 177 has the following lines concerning Rhun’s death:
“Rhun ab Alun Dyfed who was buried on the edge of the Hard (or Difficult) Ford in the Gwynfynydd in Penllyn. And there he was killed when he retreated from Ciltalgarth.”
The Ymddiddan Myrddin a Thaliesin mentions both poets lamenting the death of warriors in a battle which occurred in Dyfed against Maelgwn. It would seem that Rhun perished in this conflict. The location of Gwyn Mynydd is near Ganllwyd in Gwynedd.
Gwyn Mynydd has possibly the same meaning as Ben Nevis. Gaelic ‘Beinn’ means ‘mountain’ and ‘Niamh’ (pronounced ˈniːəv) could signify ‘bright’. It, therefore, appears that the two verses of stanza 18, which are quoted above, are a continuation of the previous stanza.
The ‘Fourth Branch of the Mabinogion’ mentions the combat between the Demetian Pryderi and the Venedotian Gwydion in which the former was killed. This story places the event at Y Felenrhyd and may be a reference to the same conflict.
BBC Englynion y Beddau stanza 24 refers to the same ford (W. rhyd):
“Piev y bet in Rid Vaen Ked
ae pen gan yr anvaered?
Bet Run mab Alun Diwed.”
“Whose is the grave at Rhyd Faen-ced
With its head downhill?
The grave of Rhun son of Alun Dyfed.”
Dyfyr, another son of Alun Dyfed, is mentioned in Geraint ac Enid as having accompanied Geraint from Arthur’s court to Erbin in Cornwall and Breuddwyd Rhonabwy tells us he was one of Arthur’s counsellors. Culhwch ac Olwen mentions that a son of Alun Dyfed was needed for tht hunt for Twrch Trwyth for unleashing the dogs. The BBC Englynion y Beddau stanza 25 mentions Alun Dyfed’s father, Meigen, whose father’s name is given in stanzas 17 to 19. Meigen’s other sons, Eiddew and Eidal, are mentioned in stanzas 46 and 47.
 Arch. Camb. Parochialia (Part 1), 155.
 Jones, T., 1967, 136, 137.
 Bartrum, P.C., 2009, 642.
 Jones, T., 1967, 122, 123.