With the support of the Prince of Powys Madog ap Maredudd and Owain's brother Cadwaladr ap Gruffydd (whom Owain had recently stripped of his lands in Ceredigion), Henry led an army consisting of one-third of the knights in England[7] and an unknown number of infantry into northern Wales and sent a fleet (led by Henry FitzRoy) to capture Anglesey to cut off Owain's supplies.

Owain's army made camp at Basingwerk to block the route to Twthill at Rhuddlan.

Owain split his army and decided to personally lead an extra 200 men into the Ewloe woods to reinforce his sons.

When Henry's outflanking force advanced into the wood, they were ambushed by Owain's forces and defeated: the Constable of Chester, Eustace fitz John, was killed, and Henry of Essex deserted the field leaving the king for dead.

Not wishing to engage the Angevin army directly, Owain repositioned himself first at St. Asaph, then further west, clearing the road for Henry II to enter into Rhuddlan "ingloriously".