"Our goal is not an exhaustive history of Europe, Ireland and the UK, but some history is useful when interpreting where people came from, when they settled and how this might be useful for the interpretation of modern DNA studies of these people. - Jim Sims, 2006"

The Belgae (Belgians) are believed to have crossed the channel about 75 BC and settled in southern and eastern portion of the isle. The Catuvallauni of Britannia had skirmished with Julius Caesar in 55 and 54 BC when Caesar raided southern Britannia to punish the tribes aiding their kin on the continent as Caesar conquered Gaul.

The most numerous tribe of the Belgae in Britannia at the time Gnaeus Julius Agricola was governor of Britannia (78-84 AD) were the Catuvallauni.

The governor Gnaeus Julius Agricola, father-in-law to the historian Tacitus, conquered the Ordovices in 78 (northern Wales). With XX Valeria Victrix, Agricola defeated the Caledonians in 84 at the Battle of Mons Graupius, in what is today northern Scotland.

This marked the high tide mark of Roman territory in Britain; shortly after his victory, Agricola was recalled from Britain back to Rome, and the Romans retired to a more defensible line along the Forth-Clyde isthmus, freeing soldiers badly needed along other frontiers.

The Roman walls shown on the map were constructed with two main purposes in mind: to prevent raiders from the north from moving cattle and wagons northward after a raid (due to a ditch built on the southside of the wall); and as part of a system of military works that could allow the Roman army to patrol the frontier.

The Antonine Wall had a short useful life compared to Hadrian's Wall, as its distance from the main areas of re-supply (in the south) proved a severe hindrance. In those days, a garrison would need a year's worth of food to wait out a siege. It was a matter of who starved first: defenders or attackers.

The Romans employed many different peoples in their military. It is possible that these foreigners left some genetic legacy as armies are want to do. Some possible sources of extra-Britannic Y-chromosomes:

• Legions of 43 AD initial conquest, about 20,000 men:
  • I Augusta
  • IX Hispania
  • XIV Gemina
  • XX Valeria Victrix
• Sarmation cavalry in 175 AD - Sarmations were a multi-ethnic peoples that lived in the area on the nothern shores of the Black Sea. Force was about 5,500 men, but hard to tell how many were Sarmation.
• Vandals and Burgundians around 278 AD

By the third century AD, the Roman empire was once again in the throws of a civil war on the continent. Commanders of Roman legions revolted and two established their own short lived states: The Gallic Kingdom of Postumus and the Kingdom of Palmyra.

Vandals and Burgundians in the service of the Roman army crossed the channel to put down an attempted revolt around 278 AD.

Amid continuing civil wars, the Romans quit Britannia about 410 AD.