Portchester Castle : this castle Hampshire on England's south coast began life as a Roman coastal fort, one of their Saxon Shore forts, but it also contains medieval additions which extended its working life across a millennium.

Portus Adurni

Portus Adurni was a Roman fortress in the Roman province of Britannia. It is the best preserved Roman fort north of the Alps. The fort was built during the 3rd century as part of the Saxon Shore Forts to protect the southern coastline of Britain, possibly from Saxon raiders. It occupies a commanding position at the head of Portsmouth Harbour.

The Saxon shore forts, including Portus Adurni, were built during the mid to late 3rd century amid increased instability in north-eastern Gaul and the Rhineland, eventually leading to the Roman evacuation of that area. The forts were intended to maintain control over the region, and monitor shipping and trade, as well as defending against raids from across the English Channel.

Portchester Castle

Portchester Castle (Hampshire, England), is a medieval fortress that was developed within the walls of the Roman Saxon Shore fort of Portus Adurni. A plot to overthrow Henry V was discovered and the culprits apprehended at Portchester; this event features in Shakespeare's play, Henry V.