Portchester castle began life as a Roman fortress, probably constructed towards the end of the 3rd Century to protect the southern coastline and trade routes from Saxon raiders. After the departure of the Romans, the fortress remained in use as an Anglo-Saxon residence.

In 1086, the noble William Maudit took possession of the fortress, and began work building a Norman castle inside the original Roman walls, tucked away in the north-east corner. The Norman structure was a one-story keep surrounded by a wooden palisade.

The keep was extended during the 12th Century, eventually rising to four stories in height. In 1130AD, William Pont de l'Arche acquired the castle, and founded a priory in the south-east corner of the Roman precinct. By 1180AD, the wooden palisade had been replaced with a stone wall. By this time, the castle had reverted to the crown, and was often used as a place of residence by English kings.

Subsequent decades saw further expansion at Portchester, but it was during the 14th Century that major rebuilding took place, as the castle's position became increasingly important during the Hundred Year War with France. In 1346AD, King Edward assembled an army of 12,000 to 16,000 men at Portchester, before departing for the Battle of Crecy. In 1415AD, Henry V conducted a fleet review at Portchester before heading on to the Battle of Agincourt.

Following the end of the Hundred Year War, Portchester's prominence declined. This process was hastened when Henry VII constructed the royal dockyard at neighbouring Portsmouth.

During the 17th century, Sir Thomas Cornwall undertook further building work at Portchester, with the emphasis on the castle as a place of residence rather than a fortification.

The Napoleonic Wars of the 19th Century saw Portchester pressed into service as a hospital, a barracks, and most notably a gaol housing 7000 French prisoners of war. This latter role is responsible for Portchester surviving in such an exceptional state of repair.

Today, the most striking feature at Portchester is the outer wall. It encloses a vast area (around nine acres), and survives in superb condition. Despite later repairs and additions, the wall is essentially Roman, and the best-surviving example of its kind in the whole of northern Europe.

Access to the bulk of the fortification is free, but a charge is levied for access to the Norman castle - but this really does represent a mere fraction of this historic site.

2,000 years of continuous use are evident at Portchester, representing a truly unique piece of heritage. The grounds are frequently busy, but the abundance of space prevents any sense of crowding. This is a site well worth visiting, and you won't find its equal anywhere else in Britain.