Battle of Llandeilo Fawr
1282 CE.
Shown on the map at 51.884°, -3.996°.
The Battle of Llandeilo Fawr took place during the conquest of Wales by Edward I, at Llandeilo between an English army led by Gilbert de Clare, 6th Earl of Hertford, and a South Welsh army led by Rhys ap Maredudd.
Text from the Wikipedia article Battle of Llandeilo Fawr, licensed CC BY-SA 4.0.