The hunt for Trwch Trwyth starts in Ireland. Arthur's men disturb the pig in Esgeir Oervel, and it comes over to Wales to cause havok - leading Arthur a merry dance across southern Wales*. It lands at Porth Cleis in Dyved (Porth Clais, an inlet south of St. David's**: Info). Arthur then chases it on the following route** (Map):
occupied a central area between the mountains Llanddewi Velfrey, Henllan Amgoed, and Laugharne: it probably covered portions of the parish of Whitland and of that of Llandysilio, the church of which is a little to the north of the railway station of Clyn Derwen[Clunderwen];
Clyn Ystun, now written Clun Ystyn ... a farm between Carmarthen and the junction of the Amman with the Llychwr [Loughor: at Pantyffynnon*], more exactly about six miles from that junction and about eight and a half from Carmarthen as the crow flies- possibly putting it near Drefach. This is backed up by a 1609 survey of Carnwyllion which notes it as the east side of the Gwendraeth Vawr river between Carway and Mynydd Mawr*;
is now represented by a bog mere above a farm house called Llwch in the parish of Bettws, which covers the southern slope of the Amman Valley. [Though he] found this bog called in a map Llwch is Awel, 'Pool below Breeze'. This seems somewhat thin evidence. Bromwich and Evans* suggest Llangadog castle (previously Castell Luchewein), Llyn Llech Owain, the Black Mountain, or somewhere west of the mouth of the River Wye;
Llyn Llwch Towe, in Breconin 1584/5, indicating this is the old name for Llyn y Fan Fawr;
before being chased through Cornwall and into the Atlantic, never to be seen again.