Castles of the British Isles

Richborough today sits around three kilometres inland from the coast, in what are now the East Kent marshes. During the initial Roman period in the first century AD it was on the coastal edge, a small island at the southern end of the strategically important Wantsum sea channel which divided Kent from the Isle of Thanet.

It is generally accepted that the primary Roman invasion force of forty thousand men arrived here in AD 43, in what would have been a massive and highly complicated military operation.

The army quickly created a defensive barrier across the island in the form of two deep, parallel v-shaped ditches with a rampart on the seaward side. The entire construction ran for at least six hundred and fifty metres from north to south in line with the coast. This fortification served as a defensive buffer against expected initial attacks by the Britons.

Surprisingly after the stiff resistance faced by Julius Caesar almost exactly a century beforehand (see 'related links' for more on this), the Romans encountered no resistance near their landing point so that the army was able to firm up unmolested to advance inland.

After that Richborough became one of the main supply points for the campaign of conquest. Evidence has been found of large storehouses or granaries which would have provisioned the troops as they made their way inland. The base later developed into a port town which was known as Rutupiae.

The coast here at this time was very different from today. The island of Richborough stood in the wide Wantsum channel, with a narrow tidal channel between the island and the mainland. This was bridged by a man-made causeway which connected it to the soon-to-be-built Roman road of Watling Street.

The Isle of Thanet stood about three kilometres away from the mainland, separated on its western and southern flanks by the Wantsum channel. Extensive shingle banks sheltered the Wantsum from the sea, effectively forming a breakwater. This made Richborough island an ideal anchorage for the Romans, and later for Roman traders.

Over the past two thousand years that mighty channel was gradually filled in by continued silt being shifted east by the Thames estuary, which also resulted in the East Kent coast between the River Medway and Reculver losing up to three kilometres of land.

This is why Reculver's fort and medieval church now sit right up against a small coastal cliff (see 'related links'). A gradual rise in sea level has also been noted as part of this erosion process (or at least a lowering of the coast as a late result of the loss of ice age 'weight' in the north which initially would have 'tipped up' southern England).

The gradual southwards extension of the main shingle bank, the Stonar Bank, meant more silt collection behind it, which contributed to the mainland gradually shifting eastwards towards Thanet.

A shallow, muddy lagoon was formed which was surrounded by a salt marsh. Navigation became impracticable by the medieval period and Canterbury suffered somewhat as river traffic on the Stour gradually faltered and faded. Today the Wantsum is little more than a narrow stream and Thanet has been joined to the mainland. Richborough now lies three kilometres inland from the sea.

A town soon grew up around the Roman landing point and the fort which was built around it. That town included an amphitheatre and one of the biggest monumental arches in the Roman empire. Probably built sometime between AD 85-150, it was exceptionally large and elaborate.

The town reached the peak of its development in the second century. A stone rebuild took place of an earlier timber mansio (an inn for messengers and officials who were on government business), and other buildings lined the streets which included shops. The town extended far beyond the confines of the later Roman fort.

Drastic changes occurred in AD 250 in response to conflict within the empire and attacks by Saxon and Frankish raiders in the English Channel. Buildings in the centre of the town were demolished to be replaced by a small fort. Shortly afterwards this fort was replaced by another, when the monumental arch was dismantled and its materials were reused.

The second fort was built in stone between AD 275-290, and this remains the most prominent feature on the site. It formed part of a chain of coastal forts which defended the eastern and southern coasts of Britain as part of the network of 'Saxon Shore' forts.

Roman civil settlement continued here into the fourth century and Richborough seems to have remained important as the gateway into Britain.

In the last days of the Roman administration of Britain (see 'related links') it may well have been the last site within the province of Britannia to which Roman coins were supplied. Official Roman contact ended at the start of the fifth century and the fort was allowed to decay during Britain's post-Roman descent into factionalism.

One photo by P L Kessler, taken in 2025, and five kindly contributed by Greentool2002 via the 'History Files: Castles of the British Isles' Flickr group.