By 43, the time of the main Roman invasion of Britain, Britain has already frequently been the target of invasions, planned and actual, by forces of the Roman Republic and Roman Empire.

In common with other regions on the edge of the empire, Britain has enjoyed diplomatic and trading links with the Romans in the century since Julius Caesar's expeditions in 55 and 54 BC, and Roman economic and cultural influence is a significant part of the British late pre-Roman Iron Age, especially in the south.