To inform the consideration of The Inventory of Historic Battlefields in Wales, a phased programme of investigation was undertaken on the battle of Cymerau. Detailed reports of these investigations are available and comprise documentary and historical research (Chapman), and non-invasive fieldwork (Archaeology Wales).

Cymerau and the related earlier conflict at Coed Llathan took place on 2 June 1257 and marked a significant phase in the extension of the reach and power of Llywelyn ap Gruffudd (d. 1282) as Prince of Wales. Here, an English-led force of knights and predominately Welsh infantry drawn from the Marcher lordships of south and east Wales were defeated by forces led by members of the royal line of Deheubarth.

The Breviate Chronicle provides the following description:

Circa horam uero meridiei ad kemereu pugnando peruenientes et predicti walenses cum dei auxilio inter armatos anglicos irruerunt et de equis armatis inclitos saxones uiriliter prostrauerunt et eos sub pedibus ? equitum ? peditum et equorum in moris et in fossis et in uallibus conculcauerunt et plus quam tria milia saxonum in illa die occubuerunt ? pauci uero aut nulli de armacis milicibus de illo bello euaserunt (Gough-Cooper, b1278.7)

Translation: Truly about the hour of midday at Cymerau (Kemereu) the hour of battle arrived and the Welsh, with the help of God, erupted into the English. The celebrated Saxons were thrown manfully to the ground from their armoured horses and as infantry were trampled under the horses? feet, and so the knights in the bushes and the ditches and the valleys were trampled underfoot, and more than 3,000 Saxons were killed that day; for truly none or only a very few of the armoured knights escaped from this battle (Remfry, 196-7).

The scale and significance of the defeat of English forces is indicated in the frequency with which details appear in English chronicles, notably Mathew Paris's Chronica Majora and in a variety of annals maintained in English monasteries, notably Osney and Tewkesbury .

The location of Cymerau is unknown. Two possible sites have been suggested, but both are problematic and each dependent on an interpretation of where the English army was heading, in this case either Carmarthen or Cardigan. The first is at the confluence of the rivers Twyi and Cothi at SN 500 208 (Lloyd, 720) and the second at the confluences of Afon Ddulais, Afon Ddu and Nant Llwyd, two miles south east of Talyllychau at SN 645 305 (Owen).

RCAHMW (Battlefields Inventory), Jan 2017

Bibliography
Archaeology Wales, 1257 Battle of Coed Llathen and Cymerau: Battlefield Survey (2014).
Chapman, A., Coed Llathen and Cymerau,2 June 1257: Documentary and Historical Research Report (2013).
Gough-Cooper, Henry (ed.) The Breviate Chronicle: Annales Cambriae, The B Text from London, National Archives, MS E164/1, pp. 2?26, online edition.
Lloyd, J. E,, A History of Wales from the Earliest Times to the Edwardian Conquest, third edition (Longmans, Green, London, 1939).
Owen, Henry (ed.), The Description of Penbrokeshire by George Owen of Henllys Lord of Kemes, vol 4, Cymmrodorion Record Series no. 1 (London,1936).
Remfry, Paul M. Annales Cambriae: A Translation of Harleian 3859: PRO E. 164/1: Cottonian Domitian, A1: Exeter Cathedral Library MS.3514 and MS Exchequer DB Neath, PRO E. 164/1 (Castle Studies Research, 2007).