Portus Adurni

[4] Portus Adurni may be identical with the Ardaoneon listed in the Ravenna Cosmography,[3] and Rivet and Smith derive both names from the British "ardu-" meaning "height".

The gates of Portus Adurni are of particular interest: they are indented inwards, so as to trap the enemy in an area exposed to walls on three sides; this technique became widely used from the Augustinian age to the fall of the Empire.

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.

These forts became defensive holding points for the rebel Carausius, who in 285 was given the task of solving the Saxon piracy problem in the English Channel.

The revolt went on for almost 10 years while other Roman generals tried and failed to dislodge him, until he was eventually murdered by Allectus, one of his aides, in 293, and Britain was finally taken back by 296.