Londinium

• 1. Introduction

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  Londinium stood at the edge of the known world, a Roman city planted on a damp, river-cut plain at the far northwestern reach of the empire. Its earliest securely-dated structure is a timber drain, dug beside the main Roman road in 47 AD. From that modest beginning, the city would grow to house perhaps as many as sixty thousand people, host the empire's largest basilica north of the Alps, and outlast its founders by more than a millennium in the form of the London Wall. How did a private-enterprise trading post become the capital of Roman Britain? What brought it to the height of power under Hadrian's gaze in 122, and what eroded it by the time the last wealthy families were quietly importing luxuries from a collapsing empire?

• 2. A City Born from Trade

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  Unlike many of its contemporaries in Roman Britain, Londinium was not planted on top of an existing native settlement. Archaeologist Lacey Wallace has noted that because no Late Pre-Roman Iron Age settlements or significant domestic refuse have been found in London despite extensive excavation, arguments for a purely Roman foundation are now common and uncontroversial. The surrounding territory had been contested between two powerful tribes, the Catuvellauni to the west and the Trinovantes to the east, but the site itself appears to have been open rolling countryside threaded by streams.

  What the location offered was water. The point on the River Thames where Londinium was built was narrow enough to bridge yet still deep enough to handle seagoing ships. Its position on the Tideway gave vessels sailing upstream a fighting chance. The remains of a massive pier base for such a bridge were found in 1981 close by the modern London Bridge. That bridge made the city a road nexus almost immediately: of the fifteen British routes recorded in the Antonine Itinerary, seven ran to or from Londinium.

  Tacitus captured the city's essential character when he described it at the time of Boudica's uprising as a place that, though undistinguished by the name of colony, was much frequented by a number of merchants and trading vessels. Archaeologists have confirmed this picture by uncovering numerous imported goods from across the Roman Empire in the city's earliest layers, suggesting a cosmopolitan community of merchants rather than a military garrison town. The early settlement occupied roughly 1.4 square kilometres, about the size of present-day Hyde Park.

• 3. Boudica's Fire

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  In 60 or 61 AD, the king of the Iceni died. His will had divided his kingdom between Rome and his two daughters, but Roman law forbade female inheritance and it had become common practice to annex allied kingdoms upon a ruler's death. Roman financiers, including Seneca, called in all of the king's outstanding loans at once, while the provincial procurator confiscated the property of both the king and his nobles. When the king's wife Boudica objected, Tacitus records that the Romans flogged her, raped her two daughters, and enslaved their nobles and kinsmen.

  The Iceni and their allies first overwhelmed the garrison at Camulodunum. The 9th Legion under Quintus Petillius Cerialis, marching south from the Fosse Way, was ambushed and annihilated. Gaius Suetonius Paulinus, who had been leading the conquest of Anglesey, rode back along Watling Street with the legions' cavalry and reached Londinium to find it indefensible. His words, preserved in Tacitus, remain stark: he decided to sacrifice the single city of Londinium to save the province as a whole. Those who could not or would not follow were slaughtered.

  Excavation has found the evidence beneath the modern city: a layer of red ash at this exact date. Paulinus eventually defeated the Iceni army, and the sources record that as many as seventy thousand men and camp followers were killed. A large military fort covering 15,000 square metres was then built at Plantation Place on Cornhill, its three-metre-high banks enclosed by three-metre-deep double ditches, a temporary emergency measure that was in use for less than ten years before the city was rebuilt as a planned Roman town.

• 4. Height of Empire

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  Emperor Hadrian visited Londinium in 122, and the city he found was at its peak. Its second forum, built over a period of roughly thirty years from around 90 to 120, measured 168 by 167 metres. The three-storey basilica was probably visible across the entire city and was the largest structure north of the Alps. The marketplace rivalled those in Rome itself.

  A large building near Cannon Street Station, whose foundation has been dated to this era, is assumed to have been the governor's palace. It boasted a garden, pools, and several large halls decorated with mosaic floors. It stood on the east bank of the River Walbrook near where it meets the Thames, and the London Stone may originally have been part of the palace's main entrance. The city's population at this point stood somewhere between 45,000 and 60,000, with many stone townhouses packed tightly together, piped water, and what excavations have described as a fairly sophisticated drainage system.

  Londinium's amphitheatre, constructed in 70, stood at what is now Guildhall. A marble slab excavated at a temple complex in Southwark bears a dedication to Mars and carries the inscription Londiniensi, meaning the Londoners, making it the earliest known written reference to the people of London. A separate find in Southwark from excavations in 1988 and 2021 revealed an elaborate building with fine mosaics and frescoed walls that has been dated to 72 AD. The city was not merely an administrative capital; it was, for a few generations, a genuinely grand place.

• 5. The Wall That Outlasted Rome

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  Sometime between 190 and 225, the Romans built a defensive wall around the landward side of Londinium. The wall ran approximately five kilometres, stood six metres high, and was two and a half metres thick. Its dry moat was about two metres deep and three to five metres wide. Along with Hadrian's Wall and the road network, it was one of the largest construction projects ever undertaken in Roman Britain.

  The wall had four main gates: Bishopsgate and Aldgate in the northeast, serving roads to Eboracum and Camulodunum, and Newgate and Ludgate in the west, along the roads toward Viroconium and Calleva. The wall absorbed the army's existing northwest fort, thickening its outer wall with a second course of stone to match the new construction. The riverbank was initially left undefended; that gap was corrected in the 3rd century with a riverside wall running roughly along the course of present-day Thames Street.

  The reason for the wall's construction is unknown. Some historians connect it with a Pictish invasion in the 180s; others link it with Clodius Albinus, the British governor who attempted to unseat Septimius Severus in the 190s. What is certain is that the wall endured. It survived another 1,600 years and still broadly defines the perimeter of what is today called the City of London. Its gates were refurbished and replaced until their demolition in the 17th and 18th centuries to permit widening the roads. In 2023 a section of the wall at the Vine Street museum opened to the public.

• 6. Revolt, Religion, and Decline

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  In 286, the emperor Maximian issued a death sentence against Carausius, admiral of the Roman navy's Britannic fleet, on charges of having abetted piracy and embezzled recovered treasure. Carausius revolted, declared a new Britannic Empire, and issued coins. His successor Allectus held Britain until 296, when Constantius Chlorus invaded. Allectus's Frankish mercenaries sacked Londinium, and they were only stopped by a flotilla of Roman warships on the Thames. The event was commemorated by the golden Arras Medallion, which shows Chlorus on one side and on the other a woman kneeling at the city wall welcoming a mounted soldier.

  Through the 4th century, Londinium juggled religious change alongside military pressure. Either Bishop Restitutus or Adelphius attended the Council of Arles in 314, placing a Christian representative from the city at the most important ecclesiastical gathering of that era. A large and ornate building discovered on Tower Hill in 1995 was built sometime between 350 and 400; it was about one hundred metres long and fifty metres wide, constructed of stone taken from other buildings including a veneer of black marble, and was probably dedicated to St Paul.

  Meanwhile the city's defences expanded: at least twenty-two semi-circular towers were added to the walls to mount ballistae. In 367, the Great Conspiracy brought a coordinated invasion of Picts, Gaels, and Saxons, and Count Theodosius used Londinium, by then known as Augusta, as his base for the years-long recovery effort. The Antonine Plague, which swept Western Europe between 165 and 190, had likely already halved the population; by the second half of the 2nd century Londinium had begun to shrink, and the dark earth that archaeologists find covering much of the later city tells its own story of a settlement contracting inward.

• 7. The Long Abandonment

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  Between 407 and 409, large numbers of barbarians overran Gaul and Hispania, severing reliable communication between Rome and Britain. Trade broke down, officials went unpaid, and Romano-British troops elected their own leaders. Constantine III declared himself emperor and crossed the Channel; Emperor Honorius subsequently directed the Britons to look to their own defence. Excavations of the port show signs of rapid disuse around this period.

  A small number of wealthy families continued to maintain a Roman lifestyle until the middle of the 5th century, inhabiting villas in the southeastern corner of the city and importing luxuries, according to archaeological evidence. The Anglo-Saxon Chronicle records that the Britons fled to Londinium in terror after their defeat at the Battle of Crecganford, probably modern Crayford, but says nothing further about what happened inside the walls. By the end of the 5th century, the city was largely an uninhabited ruin, its large church on Tower Hill burnt to the ground.

  The Saxon settlement of Lundenwic that followed was not planted within the Roman walls but to the west, in the area now called Aldwych. It was only the Viking invasions of England that prompted King Alfred the Great to move the settlement back inside the safety of the old Roman perimeter, giving it the name Lundenburh. The river wall's foundations were undermined over time and had completely collapsed by the 11th century, but the landward wall held, and its outline determined the shape of the city that grew up around it. The 9th-century History of the Britons still counted it among the twenty-eight cities of Britain, remembered as Cair Lundem.