The story of Portchester
Through the 3rd century, Saxon pirates raided the south and east coasts of Roman Britain, and a chain of coastal forts went up against them. They are now called the Forts of the Saxon Shore. Portchester is the best-preserved Roman fort north of the Alps.1
The rebel admiral
No inscription dates the fort, but coins found on the site show it was built after about AD 268, probably between 285 and 290. That points to one man. In about 285 the emperor Diocletian gave Marcus Aurelius Carausius command of the Roman fleet in the Channel. When the co-emperor Maximian condemned him to death, Carausius rebelled with his fleet behind him and declared himself emperor of Britain and northern Gaul. A fort at the head of a great harbour is just what his fleet needed. In 293 his deputy Allectus murdered him, and within a few years Britain was back in the empire.1
The fort was laid out symmetrically, with a gate in the middle of each side and 20 D-shaped towers spaced evenly around it. Sixteen still stand. The walls rise to 6.1 metres, though the top parts were rebuilt in the Middle Ages.1
Families inside the walls
It was not only soldiers. Archaeologists found timber houses and workshops inside the walls, with animal pens, cesspits and rubbish heaps, and the burials of 27 babies. That means families lived here too. The fort seems to have been in use right up to the end of Roman Britain in the early 5th century.1
After Rome
The walls kept people in for centuries more. In the 5th century there were four huts with sunken floors, a well and ploughed ground. In the 7th to 9th centuries came timber houses, then a break, with rubbish dumped over the old buildings. In 904 the Bishop of Winchester gave the fort to King Edward the Elder, who made it a burh, a fortified town against the Vikings. By the 10th century an important family lived here in a large hall with a stone tower.1
After 1066 the Normans built a castle in one corner of the Roman fort. Kings used it on their way to France: Henry V set off from here in 1415 for the campaign that ended at Agincourt. From 1665 to 1814 the castle held prisoners of war, up to 8,000 at a time during the wars with France.1
Where the evidence is unclear
Was it really Portus Adurni?The name comes from the Notitia Dignitatum, whose date is itself disputed, somewhere between AD 380 and 420. Portchester is the favourite, not a certainty.1
Did Carausius build it?The coins say after about 268, and the harbour fits a fleet. But no inscription names its builder, so his part is a strong guess.1
