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):

Menevia - the old name* for St.Davids*;
Deu Gleddyf
Deugleclyf: Aberdaugleddau: Milford Haven* or that region* ;
Pres(/c)elly: area of the Prescelly Mountains in northern Pembrokeshire*;
o deu tu Nyuer* (Glyn Nyver*)
The two banks of the Nyfer: Uch Nyfer and Is Nyfer the two sections of the Cemais(/es) cantref divided by the river Nyfer*. Valley of the Nyfer or the river Nevem*: Info;
Cwm Kerwyn
Foel Cwm Kerwyn [Cwmcerwyn], one of the Preselly heights*;
Rhys* estimates this as having 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];
Aber Tywi*;
Glyn Ystu(n)
Rhys* suggests 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*;
Dyffryn Llychwr
Valley of the Llychwr or Loughor* from Ammanford downstream to Pontarddulais*;
Mynydd Amanw
Rhys* suggests Amanw is Amman/Aman/Amann. This is a common name in the Black Mountain area suggesting this is the region referred to* Rhys* specifically suggests around Bryn Amman [Brynamman]. There may be a link with the Welsh word banw (apparently "sow"?)*;
Dyffryn Amanw
Dyffryn Amman "Valley of the Amman"* [Cwm Aman];
Llwch Ewin
Lake of Ewin: Rhys* speculates that this 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;
Llwch Tawy
Bromwich and Evans* note that the origin of the Tawy is noted as Llyn Llwch Towe, in Brecon in 1584/5, indicating this is the old name for Llyn y Fan Fawr;
between Tawy and Euyas
The River Tawy??? and Ewias - a cantref ~ south of Hereford* (now probably only represented by the village name Harold Ewyas [area]);
Severn between Llyn Lliwan and Aber Gwy
For Llyn Lliwan see Wonder 6. Aber Gwy is the mouth of the Wye;

before being chased through Cornwall and into the Atlantic, never to be seen again.