City of London: History
=== Origins ===
The Roman legions established a settlement known as "Londinium" on the current site of the City of London around AD 43. Its bridge over the River Thames turned the city into a road nexus and major port, serving as a major commercial centre in Roman Britain until its abandonment during the 5th century. Archaeologist Leslie Wallace notes that, because extensive archaeological excavation has not revealed any signs of a significant pre-Roman presence, "arguments for a purely Roman foundation of London are now common and uncontroversial."
At its height, the Roman city had a population of approximately 45,000–60,000 inhabitants. Londinium was an ethnically diverse city, with inhabitants from across the Roman Empire, including natives of Britannia, continental Europe, the Middle East, and North Africa. The Romans built the London Wall some time between AD 190 and 225.
The boundaries of the Roman city were similar to those of the City of London today. The City extends further west than Londinium's Ludgate, and the Thames was undredged and thus wider than it is today, with Londinium's shoreline slightly north of the City's present shoreline. The Romans built a bridge across the river, as early as AD 50, near to today's London Bridge.
By the time the London Wall was constructed, the City's fortunes were in decline, and it faced problems of plague and fire. The Roman Empire entered a long period of instability and decline, including the Carausian Revolt in Britain. In the 3rd and 4th centuries, the City was under attack from Picts, Scots, and Saxon raiders. The decline continued, both for Londinium and the Empire.
In AD 410 the Romans withdrew entirely from Britain. Many of the Roman public buildings in Londinium by this time had fallen into decay and disuse, and gradually after the formal withdrawal the City became almost, if not, at times, entirely uninhabited. The centre of trade and population moved away from the walled Londinium to Lundenwic ("London market"), a settlement to the west, roughly in the modern-day Strand/Aldwych/Covent Garden area. …