Castles of the British Isles

Portchester Castle sits at the mouth of Lake Paulsgrove, at the south-eastern corner of the village of Portchester, and to the east of Fareham in Hampshire on England's south coast.

The initial fortifications were built by the Romans, as one of their Saxon Shore forts. The name Portus Adurni appears only once in surviving Roman records, on the Notitia Dignitatum where it falls under the command of the 'Right Honourable Count of the Saxon Shore in Britain' (see 'related links', below), but it is common practice to match the name to Portchester.

While 'portus' means 'port', the name 'Adurni' would seem to come from the Brythonic 'ardu-', meaning 'height'. This would refer to the nearby Portsdown Hill which overlooks the village and harbour.

In the third century AD, Saxon, Pictish, and Scotti (Irish) pirates began to raid the coasts of Roman Britain. After taking some time to adjust to this new, unsettled situation, the Romans maintained a fleet in the English Channel and the North Sea which was supported by a series of forts and watch towers around the coast.

This was the Saxon Shore.

Archaeology at Portchester suggests that the fort here was built between AD 285-290, on the orders of the Roman commander of the fleet, Marcus Aurelius Carausius.

In AD 286 he found himself at the wrong end of accusations of collusion with the raiders - they raid responsibly and he collects a tithe from their gains - so he was left with no choice but to rebel.

He proclaimed himself emperor of Britain and parts of Gaul in the style of the recently-collapsed 'Empire of the Gallic Provinces', forming a stand-alone Roman empire in the north-west of Europe.

In AD 293 Rome won back its territory in Gaul and, later that year, Carausius was assassinated by a follower named Caius Allectus, who briefly ruled Britain in his place before being defeated and killed.

The province was brought back under Roman control in AD 296 following a full-scale invasion by General Asclepiodotus.

Roman forces used the fort occasionally, although the archaeology shows that it was generally occupied by a civilian population (quite possibly at the same time). Within its walls they built timber houses and workshops which were surrounded by animal pens, cesspits, and rubbish heaps.

The castle walls are topped with a medieval walkway which was not present in the Roman period. As its outer walls remain almost fully intact, Portus Adurni is the best-preserved Roman fort north of the Alps.

The castle was captured from the Britons by newly-arrived Saxons in AD 501, according to the Anglo-Saxon Chronicle. They kept the name, Portus, but added 'chester' to the end to signify a fortified location, which supplies today's name of Portchester.

The medieval fortress which survives within the Roman walls was developed following the arrival of the Norman King William in 1066. The keep was probably built in the late eleventh century as a baronial castle.

Portchester was taken under royal control in 1154, as Henry II Plantagenet gained the throne. The monarchy controlled the castle for several centuries and it was a favoured hunting lodge of King John.

It was besieged and captured by the French in 1216 during an attempted invasion following the death of King John. This was thwarted, largely by William Marshal, regent for the young Henry III.

Occupying a commanding position at the head of Portsmouth Harbour, medieval Portchester remained an important port. The castle was the embarkation point for several campaigns into France which were led by England's kings.

In anticipation of a fresh French invasion during the first quarter of the fourteenth century, Edward II initiated repairs and reinforcing of the castle.

A plot to overthrow Henry V was discovered and the culprits apprehended at Portchester. This event features in Shakespeare's play, Henry V. Later in its history, the castle was used as a prison.

Today Portchester Castle is a 'Scheduled Ancient Monument', and a Grade I listed building. It has been in the ownership of the Southwick Estate since the seventeenth century but is managed by English Heritage and is open to visitors throughout the year.

The Norman church, St Mary's, which stands in the south-east corner of the grounds, is administered by the Anglican diocese of Portsmouth.

Eight photos on this page kindly contributed by Guy Fogwill, via the 'History Files: Castles of the British Isles' Flickr group.