Claim: Einion ap Collwyn persuaded Robert FitzHamon, lord of the honour of Gloucester, and twelve other knights, to bring a army to the aid of Iestyn, which led to the fall of the kingdom of South Wales.
Evidence: He persuaded Robert FitzHamon, historically lord of the honour of Gloucester, and twelve other knights, to bring a great army to the aid of Iestyn. Rhys was slain by them in a terrible battle near the boundaries of Brycheiniog, at Hirwaun Gwrgan. With Rhys fell the kingdom of South Wales.