[1] The battle was fought near Penparc, northeast of Cardigan, probably on the hill now known as Banc-y-Warren; it resulted in a rout of the Norman forces, setting back their expansion in West Wales for some years.

He had not gone far when he was ambushed and killed by the men of Iorwerth ab Owain, grandson of Caradog ap Gruffydd (the penultimate prince of Gwent).

The Royal Commission on the Ancient and Historical Monuments of Wales puts the site of the battle on the southeast slopes of Banc y Warren (or Banc-y-Warren), a prominent conical hill near Penparc, 2 miles (3.2 km) northeast of Cardigan.

[7] Gerald of Wales, in his Itinerarium Cambriae of 1191, describes (56 years after the battle):We proceeded on our journey from Cilgarran towards Pont-Stephen, leaving Cruc Mawr, i.e. the great hill, near Aberteivi, on our left hand.

On this spot Gruffydh, son of Rhys ap Theodor, soon after the death of King Henry I, by a furious onset gained a signal victory against the English army...[8] Members of Gerald's family were participants in the battle.

Edward Laws quotes Florence of Worcester (vol iii, p. 97): ...the slaughter was so great that besides the male prisoners there were 10,000 widows captured, whose husbands had either been slain in battle, burnt in the town, or drowned in the Teivi.

No contemporary source on the battle mentions bows, but the victory at Crug Mawr took place at a time when the south-eastern Welsh were using longbows as a weapon of war; in 1188, Giraldus Cambrensis noted that the bowmen of Gwent used long powerful bows, attributing the defeat and death of Richard Fitz Gilbert de Clare to Welsh bowmen earlier in 1136.

[14][15] In 2018, the leader of Plaid Cymru, Adam Price suggested that the longbow was a feature of the battle, arguing that the Norman threat led the Welsh to innovate a new solution.

In Deheubarth, Gruffydd ap Rhys died in uncertain circumstances in 1137, and the resulting disruption allowed the Normans to partially recover their position in the south.