A military installation at Portchester dates back to Roman times. Excavations have revealed what was probably a base for the Classis Britannica, the Roman fleet based in the UK. It probably dates from 285-290 AD. The remains of the curtain wall of this base can be seen at Portchester today.
The fort continued in use after the Romans left Britain, as evidenced by the presence of a 10th century Anglo-Saxon hall within the walls and in 904 records show the castle passed into the ownership of the crown. The castle as we see it today dates from the 11th century and was built by William Maudit. He sought where possible to include as much as possible of the still-standing Roman walls within his construction. In 1154 the castle passed to King Henry II and it would remain in royal control for almost 500 years. King Henry and King John were recorded as visitors and it was used to house important prisoners. In 1216, Portchester surrendered to Prince Louis of France, who commanded the French forces supporting the Barons rebelling against King John. It was recaptured by John’s son, Henry III the following year and eventually, the French forces left Britain a few months later. Portchester was important as it was an embarkation point for troops going to France to defend the royal lands there.
The castle was refortified by Edward II in the fourteenth century and it continued to be used by armies campaigning on the continent. Queen Elizabeth, I visited the castle in 1603.
In 1632 Charles I sold the castle to Sir William Uvedale. It was used as a prison, often with prisoners of war from the Anglo-Dutch war (1665-1667), the War of Spanish Succession (1702-1712) and the Napoleonic Wars (19th century).