Though there were prehistoric settlements throughout the vast area that we now call London, no evidence has yet been found for any such community at the northern end of London Bridge where the present city grew up. The origins of what we now call london lie in Roman times.

Prior to the Roman invasion there was no permanent settlement of significance on the site of London. Instead, the Thames River flowed through marshy ground sprinkled with small islands of gravel and sand. After a failed attempt to conquer Britain in 56 BC under Julius Ceasar, the beginnings of London can be accurately dated to the second invasion of the Romans in AD 43 under the Emperor Claudius.

When the Romans invaded Britain in AD 43 under the command of Aulus Plautius, they moved north from the kent coast and crossed the thames in the london region, clashing with the local tribesmen just to the north of london. The soldiers first crossed the thames at lambeth, but it was further downstream that they built the first permanent wooden bridge over the river, just east of the present london bridge, in more settled times around seven years later.

As a focal point of the Roman road system, it was the bridge which attracted settlers and led to london's growth. A new network of roads which soon spread out like a fan from the crossing place. Though the uniform regularity of london's original street grid indicates that the initial inhabitants were the military, trade and commerce soon followed. The thames is deep at london and still within the tidal zone, which makes it an ideal place for berthing ships. The area was also well-drained and low-lying with geology suitable for brickmaking.

There was soon a flourishing city called Londinium in the area where the monument now stands. The name itself is Celtic, not Latin, and may originally have referred merely to a previous farmstead on the site.

However, in AD 60 Boudicca, queen of the Iceni tribe of present-day East Anglia, launched her rebellion against the new rulers of Britain. The new trading centre of London was one of her primary targets.

The governor, Suetonius Paulinus, who was busy exterminating the Druids in North Wales (the Roman's were extremely fearful of their mystical and superstitious rites), marched his troops south in an attempt to save London but, seeing the size of Boudicca's approaching army (thought to be as many as 200,000), decided he could not mount an adequate defence with the 15,000 troops he had at hand and he evacuated the city instead. Not everyone managed to escape though and many were massacred. The city was burnt to the ground.

London was quickly rebuilt, with a cluster of timber-framed wooden buildings surrounding the imposing Roman civic buildings. The city continued to grow in size and splendor over the next century, reflecting the increasing importance of trade in Britain.

From around AD 250 an altar inscription records that Governor Marcus Martiannius Pulcher rebuilt the Temple of Isis in the city; and a speculator, from his or a subsequent governor's staff, was buried on Ludgate Hill. An elaborate late 1st century building, with large reception rooms and offices, has been partially excavated beneath Cannon Street Station. It may have been the Governor's Palace. A second palatial building was recently discovered in the smaller trading settlement at Southwark, in the marshes south of the river.

The financial and economic equivalent of the governor was the procurator and there is clear evidence that the offices of this official lay somewhere within the city of Roman London. The Procurator, Gaius Julius Alpinus Classicianus who rebuilt the city after Boudicca's rebellion and promoted London trade, died and was buried there. Parts of his monumental tombstone have been dug-up and are on display in the British Museum.

The major symbol of Roman rule was the Temple of the Imperial Cult. Emperor worship was administered by the Provincial Council whose headquarters appear to have been in London by AD 100. A member of its staff, named Anencletus, buried his wife on Ludgate Hill around this time.

Pagan worship flourished within the cosmopolitan city. A temple to the mysterious Eastern god, Mithras, was found at Bucklersbury House and is displayed nearby. Traditionally, St. Paul's stands on the site of a Temple of Diana.

Other significant buildings also began to appear in the late 1st century, at a time when the city was expanding rapidly. The forum (market-place) and basilica (law-courts) complex, at Leadenhall Market, was erected and then quickly replanned as the largest such complex north of Alps. The forum was much bigger than today's Trafalgar Square.

Procurator Agricola encouraged the use of Bath Houses and a grand public suite has been excavated in Upper Thames Street. There was a smaller version at Cheapside and, in later centuries, private bath houses were also built. Another popular attraction was the wooden amphitheatre erected on the north-western outskirts of the city. It is possible that gladiatorial shows were put on here, though lesser public sports, like bear-baiting, may have been more regular.

By the early 2nd century, London had spread west of the Walbrook and a military fort was erected near the amphitheatre which itself was rebuilt in stone. This may have been in anticipation of a visit from the Emperor Hadrian in AD 122.

By about AD 200, the administration of Britain was divided in two. York became the capital of 'Britannia Inferior' & London of 'Britannia Superior'. Around the same time the city also acquired its famous walls (probably about 20ft or 7 metres high). This protective measure may have been due to civil war, initiated when Governor Clodius Albinus tried to claim the imperial crown in Rome.

For well over a millennium the shape and size of London was defined by this Roman wall. The area within the wall is now "the City", London's famous financial district. Traces of the wall can still be seen in a few places in London.

A century later, the Emperor Diocletian again reorganised Britain to improve administrative efficiency. London became the capital of Maxima Caesariensis, one of the four newly created provinces. It remained the financial centre of Britain, home of the treasury, and the usurping British Emperor Carausius established a mint there in AD 288.

Carausius was soon murdered by his finance minister, Allectus. The latter employed Frankish mercenaries who besieged London and then proceeded to plunder it. Just in time, the true Emperor's general, Constantius Chlous, arrived, with a fleet of ships, to save the city & reunite Britain with Rome.

Details of late Roman London, and Britain as a whole, are few. Christianity appears to have reached the province at an early date and, only a year after the religion became officially tolerated in the Empire, London had its own Bishop, Restitutus, who is known to have attended the Imperial Council of Arles.

Less welcome newcomers may have led to the addition of catapult towers along the city defences around AD 350. Picts and Irishmen were certainly invading Southern Britain eighteen years later. The Emperor Julian sent his general Theodosius to expel them and he used London as his headquarters. Soon afterward, the city's prestige was increased by its renaming as Augusta.

Another British usurper, Magnus Maximus, claimed the Western Imperial throne in AD 383. He is also known to have set up a mint in London and it was probably from the city that he left, with much of the Roman army stationed in Britain, for his lengthy campaigns on the Continent.

Five years later, Maximus was dead and Imperial power was waning in the extreme western provinces. Germanic style buckles, of circa AD 400, found in the city indicate that, as in other British towns, london officials were employing saxon mercenaries. London was arranging its own defence and, only ten years later, the Emperor Honorius renounced his responsibility for the British Provinces.

London had grown under the late Roman Empire, and at its peak the population probably numbered about 45,000. But, as the Roman Empire creaked its way to a tottering old age, the troops defending London's trade routes were recalled across the Channel, and the city went into a decline which lasted several centuries, a period of history known as the Dark Ages London.