Hampshire tribes of northeastern Gaul - whether these two events are linked to the decline of hillforts is unknown. By the Roman conquest, the "oppidum" at Venta Belgarum, modern-day Winchester, was the "de facto" regional administrative centre; Winchester was, however, of secondary importance to the Roman-style town of Calleva Atrebatum, modern Silchester, built further north by a dominant Belgic polity known as the Atrebates in the 50s BCE. Julius Caesar invaded southeastern England briefly in 55 and again in 54 BCE, but he never reached Hampshire. Notable sites from this period include Hengistbury Head (now in Dorset), which was a major
Venta Silurum to the emerging Kingdom of Gwent (called initially "Kingdom of Guenta"), and the town itself became known as "Caer-went" or "the castra/fort of Venta/Gwent". Tradition holds that Caradog Freichfras of Gwent moved his court from Caerwent to Portskewett around the 6th century. The town lacked substantial defences until the mid 4th century when stone town walls were built. A small garrison may have been based in the town during this period. Large sections of the defensive walls are still in place, rising up to 5 metres in height in places. The walls have been described as "easily the most impressive