Londinium, situated on a terrace near the north bank of the tidal River Thames, forty miles (sixty-four kilometers) from its estuary on the North Sea, is established as a town by the Romans after the invasion of CE 43 led by the Roman Emperor Claudius.

Archaeologists now believe that Londinium was founded by CE 50 as a civilian settlement or civitas.

A wooden drain by the side of the main Roman road excavated at No. 1 Poultry has been dated by dendrochronology to CE 47, which is likely to be the foundation date.

Before the arrival of the Roman legions, the area was almost certainly lightly rolling open countryside traversed by streams such as Walbrook.

Londinium is established at the point where the Thames is narrow enough to build a bridge, but deep enough to handle seagoing marine vessels.

Remains of a massive Roman pier base for a bridge will be found in 1981, close to the modern London Bridge.

It was traditionally thought that Londinium started as a civilian settlement, although there is also slight evidence that there was a Roman fortress.

However, archaeological excavation undertaken since the 1970s by the Department of Urban Archaeology of the Museum of London, now called MOLAS, has failed to unearth any convincing traces of military occupation on the site, so many archeologists now believe that Londinium was the product of private enterprise.

Its site on a busy river-crossing makes it a perfect place for traders from across the Roman Empire to set up business.

The name Londinium is thought to be pre-Roman (and possibly pre-Celtic) in origin, although there has been no consensus on what it means.

It is common practice for Romans to adopt native names for new settlements.

A common theory is that the name derives from a hypothetical Celtic placename, Londinion which may have been derived from the personal name Londinos, from the word lond, meaning 'wild'.

A theory proposed by Richard Coates, which does not have widespread acceptance, suggests that the name derives from a Celticized Old European river-name forming part of the oldest stratum of European toponymy, in the sense established by Hans Krahe; Coates suggested a derivation from a pre-Celtic Plowonida — from two roots, plew and nejd, possibly meaning "the flowing river" or "the wide flowing river".

Therefore, Londinium would mean "the settlement on the wide river".

He suggests that the river was called the Thames upriver where it was narrower, and Plowonida downriver, where it is too wide to ford.

Inscriptions and graffiti found by archaeologists confirm that Latin was the local language.

It has been implied by modern scholars that many of the local people spoke the Celtic language now termed Brythonic, called lingua Gallica (Gaulish) by the Romans; this language is ancestral to Welsh, Cornish and Breton.

The status of Londinium is uncertain.

It was not the capital of a civitas, though Ptolemy lists it as one of the cities of the Cantiaci.

Starting as a small fort guarding the northern end of the new bridge across the River Thames, it will grow to become an important port for trade between Britain and the Roman provinces on the continent.

The lack of private Roman villas (plentiful elsewhere) suggests military or even imperial ownership.

Suetonius, when news of the rebellion reaches him at Anglesey, hurries along Watling Street through hostile territory to Londinium.

A relatively new settlement, founded after the conquest of CE 43, Londinium has grown to be a thriving commercial center with a population of travelers, traders, and, probably, Roman officials.

Suetonius considers giving battle here, but considering his lack of numbers, and chastened by Petillius's defeat, decides to sacrifice the city to save the province.

Londinium is abandoned to the rebels, who burn it down, slaughtering anyone who had not evacuated with Suetonius.

Archaeology shows a thick red layer of burnt debris covering coins and pottery dating before 60 CE within the bounds of Roman Londinium.

Augustus had planned invasions of Britain in 34, 27 and 25 BCE, but circumstances were never favorable, and the relationship between Britain and Rome had settled into one of diplomacy and trade.

Strabo, writing late in Augustus's reign, claims that taxes on trade brought in more annual revenue than any conquest could.

Likewise, archaeology shows an increase in imported luxury goods in southeastern Britain.

Strabo also mentions British kings who sent embassies to Augustus, and Augustus' own Res Gestae refers to two British kings he received as refugees.

When some of Tiberius's ships were carried to Britain in a storm during his campaigns in Germany in CE 16, they were sent back by local rulers, telling tall tales of monsters.

Rome appears to have encouraged a balance of power in southern Britain, supporting two powerful kingdoms: the Catuvellauni, ruled by the descendants of Tasciovanus, and the Atrebates, ruled by the descendants of Commius.

This policy had been followed until CE 39 or 40, when Emperor Caligula received an exiled member of the Catuvellaunian dynasty and staged an invasion of Britain that collapsed in farcical circumstances before it left Gaul.

When Emperor Claudius successfully invaded in 43, it had been in aid of another fugitive British ruler, this time Verica of the Atrebates.

The Romans in the ensuing years had conquered more of the island, increasing the size of Roman Britain.

Governor Gnaeus Julius Agricola, father-in-law to the historian Tacitus, had in 78 conquered the Ordovices.

With XX Valeria Victrix, Agricola had defeated the Caledonians in 84 at the Battle of Mons Graupius, in what is today northern Scotland, marking the high tide mark of Roman territory in Britain; shortly after his victory, Agricola had been recalled from Britain back to Rome, and the Romans had retired to a more defensible line along the Forth-Clyde isthmus, freeing soldiers badly needed along other frontiers.

There is no historical source describing the decades that followed Agricola's recall.

Even the name of his replacement is unknown.

Archaeology has shown that some Roman forts south of the Forth-Clyde isthmus were rebuilt and enlarged, although others appear to have been abandoned.

Roman coins and pottery have been found circulating at native settlement sites in what are now the Scottish Lowlands in the years before 100, indicating growing Romanization.

Although there is some evidence of scattered Brython settlement in the area of what is today greater London, the first major settlement had been founded by the Romans in 43, following the Roman invasion of Britain.

This settlement was called Londinium, commonly believed to be the origin of the present-day name, although a Celtic origin is also possible.

The first London had lasted for just seventeen years.

The Iceni tribe of Celts led by Queen Boudica had stormed Londinium around 61, burning it to the ground.

The next, heavily planned incarnation of the city has prospered and in 100 supersedes Camulodunum as the capital of the Roman province of Britannia.

Tiberius Avidius Quietus, a friend of Thrasea Paetus, who had been executed by Emperor Nero in 66, had been made governor of Roman Britain in about 97; he holds the post until around 100.

Well into middle age by this time, he is also a friend of Plutarch and the late Pliny the Elder.

Virius Lupus, who would have served as consul some time previously, becomes Governor or Legatus of Britannia once Severus is made emperor in 197.

Severus sends him to Britain immediately to recover the province from the rebellions that had swept it following Clodius Albinus' removal of most of the garrison to press his claim for the throne the previous year.

Severus soon purges Albinus' sympathizers and perhaps confiscates large tracts of land in Britain as punishment for their loyalty to his slain rival.

In the north, Lupus is obliged to buy peace from the Maeatae, a tribal confederation that appears to have come together as a result of treaties struck between the Roman Empire and the various frontier tribes in the 180s CE under the governorship of Ulpius Marcellus.

Fearful that they will ally with the Caledonian Confederacy and unable to secure troop reinforcements from Severus, Lupus has no choice but to pay the rebels in return for their withdrawal and the return of a few prisoners.

Lupus slowly restores the forts in the Pennines to Roman control although Hadrian's Wall will not be rebuilt until around 205.

His governorship is assisted by the arrival of Sextus Varius Marcellus as provincial procurator and in who can be seen the germ of the later division of Britain into two provinces.

The Caledonians are next mentioned in 209, when they are said to have surrendered to Severus after he personally led a military expedition north of Hadrian's Wall, in search of a glorious military victory.

Herodian and Dio wrote only in passing of the campaign but describe the Caledonians ceding territory to Rome as being the result.

Cassius Dio records that the Caledonians inflicted fifty thousand Roman casualties due to attrition and unconventional tactics such as guerrilla warfare.

Dr. Colin Martin has suggested that the Severan campaigns did not seek a battle but instead sought to destroy the fertile agricultural land of eastern Scotland and thereby bring about genocide of the Caledonians through starvation. (British Archaeology, no. 6, July 1995: Features)

According to one story from around this time, when Severus' wife, Julia Domna, criticized the sexual morals of the Caledonian women, the wife of Caledonian chief Argentocoxos replied: "We fulfill the demands of nature in a much better way than do you Roman women; for we consort openly with the best men, whereas you let yourselves be debauched in secret by the vilest".

Cassius Dio's account of the invasion reads

"Severus, accordingly, desiring to subjugate the whole of it, invaded Caledonia.

But as he advanced through the country he experienced countless hardships in cutting down the forests, leveling the heights, filling up the swamps, and bridging the rivers; 2 but he fought no battle and beheld no enemy in battle array.

The enemy purposely put sheep and cattle in front of the soldiers for them to seize, in order that they might be lured on still further until they were worn out; for in fact the water caused great suffering to the Romans, and when they became scattered, they would be attacked.

Then, unable to walk, they would be slain by their own men, in order to avoid capture, so that a full fifty thousand died.

3 But Severus did not desist until he approached the extremity of the island.

Here he observed most accurately the variation of the sun's motion and the length of the days and the nights in summer and winter respectively.

4 Having thus been conveyed through practically the whole of the hostile country (for he actually was conveyed in a covered litter most of the way, on account of his infirmity), he returned to the friendly portion, after he had forced the Britons to come to terms, on the condition that they should abandon a large part of their territory."

Severus' campaigning has made significant gains by 210, despite Caledonian guerrilla tactics and purportedly heavy Roman casualties.

The Caledonians sue for peace, which Severus grants on condition they relinquish control of the Central Lowlands.

This is evidenced by extensive Severan era fortifications in the Central Lowlands.

The Caledonians, short on supplies and feeling their position becoming desperate, re-form their alliance with the Maeatae and join their fresh offensive.

Severus prepares for another protracted campaign within Caledonia.

He is now intent on exterminating the Caledonians, telling his soldiers: “Let no one escape sheer destruction, No one our hands, not even the babe in the womb of the mother, if it be male; let it nevertheless not escape sheer destruction.” (Dio Cassius (Xiphilinus) ‘Romaika’, Epitome of, Book LXXVI Chapter 15.)

A punitive expedition led by Severus' son Caracalla is sent out with the purpose of slaughtering everyone it encounters from any of the northern tribes.

Severus meanwhile prepares for total conquest but is already ill.

Another rebellion occurs in Britain when its governor declares himself emperor.

Probus sends a Mauretanian commander, one Victorinus, to crush that attempt, which he swiftly does.

…have erected a defensive river wall at Londinium, and …

Roman Britain had seen increasing attacks in the fourth century from the Saxons in the east and the Irish in the west.

A series of forts had been built, starting around 280, to defend the coasts, but these preparations were not enough when a general assault of Saxons, Irish and ‘Attacotti', combined with apparent dissension in the garrison on Hadrian's Wall, had left Roman Britain prostrate in 367.

This crisis, sometimes called the Great Conspiracy, had been settled by Count Theodosius with a string of military and civil reforms.

Maximus, after raising the standard of revolt in Segontium in 383 and crossing the Channel, had held much of the western empire, and fought a successful campaign against the Picts and Scots around 384.

His continental exploits required troops from Britain, and it appears that forts at Chester and elsewhere had been abandoned at this period, triggering raids and settlement in north Wales by the Irish.

The appearance of hostile ‘Attacotti’ in Roman sources in the 360s corresponds chronologically with various tribal and dynastic migrations from southern Ireland and subsequent Irish settlement in Western Britain in the fourth century, in some instances possibly with Roman sanction.

Later Irish and Welsh traditions concerning these population movements preserved the names of certain tributary Irish groups, which seem to have been displaced by the expansion of the Eóganachta, the group of septs which have come to dominate Munster in the later fourth century.

Prosperity continues in Roman Britain, but the withdrawals of troops by Maximus has weakened security.

The plague reaches London in the autumn of 1348, before most of the surrounding countryside.

This had certainly happened by November, though according to some accounts as early as September 29.

Arrival in London happens by three principal roads: overland from Weymouth—through Salisbury and Winchester—overland from Gloucester, and along the coast by ship.