Archaeological evidence indicates that what was later southern Britannia was colonised by humans long before the rest of the British Isles because of its more hospitable climate between and during the various glacial periods of the distant past. The Sweet Track in the Somerset Levels is the oldest timber trackway discovered in Northern Europe and among the oldest roads inthe world, and was built in 3807 or 3806 BC.
The first historical mention of the region is from the Massaliote Periplus, a sailing manual for merchants thought to date to the 6th century BC, although cultural and trade links with the continent had existed for millennia prior to this. Pytheas of Massilia wrote of his trading journey to the island around 325 BC.
Later writers such as Plinythe Elder (quoting Timaeus) and Diodorus Siculus (probably drawing on Poseidonius) mention the tin trade from southern Britain, but there is little further historical detail of the people who lived there.
Tacitus wrote that there was no great difference in language between the people of southern Britannia and northern Gaul and noted that the various nations of Britons shared physicalcharacteristics with their continental neighbours.
Hadrian's Wall viewed from Vercovicium
 Roman Britain (Britannia)
Main article: Roman Britain
Julius Caesar invaded southern Britain in 55 and 54 BC and wrote in De Bello Gallico that the population of southern Britannia was extremely large and shared much in common with the Belgae of the Low Countries. Coin evidence and the work of later Romanhistorians have provided the names of some of the rulers of the disparate tribes and their machinations in what was Britannia. Until the Roman Conquest of Britain, Britain's British population was relatively stable, and by the time of Julius Caesar's first invasion, the British population of what was western old Britain was speaking a Celtic language generally thought to be the forerunner of themodern Brythonic languages. After Julius Caesar abandoned Britain, it fell back into the hands of the Britons and the Belgae.
The Romans began their second conquest of Britain in 43 AD, during the reign of Claudius. They annexed the whole of what would become modern England and Wales over the next forty years and periodically extended their control over much of lowland Scotland.
Main article: Sub-Roman Britain
In the wake of the breakdown of Roman rule in Britain around 410, present day England was progressively settled by Germanic groups. Collectively known as the Anglo-Saxons, these included Jutes from Jutland together with larger numbers of Saxons from northwestern Germany and Angles from what is now Schleswig-Holstein.
They first invaded Britainin the mid-5th century, continuing for several decades. The Jutes appear to have been the principal group of settlers in Kent, the Isle of Wight and parts of coastal Hampshire, while the Saxons predominated in all other areas south of the Thames and in Essex and Middlesex, and the Angles in Norfolk, Suffolk, the Midlands and the north.
The population of Britain dramaticallydecreased after the Roman period. The reduction seems to have been caused mainly by plague and smallpox. It is known that the plague of Justinian entered the Mediterranean world in the 6th century and first arrived in the British Isles in 544 or 545, when it reached Ireland. The Annales Cambriae mention the death of Maelgwn Wledig, king of Gwynedd from that plague in 547.
 Anglo-Saxonconquests and the founding of England
Main article: History of Anglo-Saxon England
Kingdoms and tribes in Britain, c.600 AD
In approximately 495, at the Battle of Mount Badon, Britons inflicted a severe defeat on an invading Anglo-Saxon army which halted the westward Anglo-Saxon advance for some decades. Archaeological evidence collected from pagan Anglo-Saxon cemeteries...