The 9th Battle was at the city of Leigion, which was called Cair Lion

The Roman city of Caerleon could well have been this battlesite, and Roman legions were housed in barracks there.

Some put forward Chester or York as alternative sites.

Caerleon (the Roman fort of Isca) was a Roman military base. Today it is a town a few miles north of Newport in southern Wales.There were Roman military barracks outside the city walls, and they can still be seen today. They are the only visible remains of Roman legionary barracks in Europe.

These barracks were built in 75 AD and each individual buildings could hold 80-100 men, the Roman century. Six centuries made up a cohort, and ten cohorts composed a legion. The Second Augustan Legion at based at Caerleon would have therefore had about 6,000 men.

The Battles of King Arthur