Britain had been the target of invasions by the Roman Republic and Roman Empire. It had diplomatic and trading links with the Romans after Julius Caesar's expeditions in 55 and 54 BC. Roman economic and cultural influence was already part of the British late pre-Roman Iron Age, in the south.
Between 55 BC and the 40s AD, Britain was not invaded. Augustus prepared invasions in 34 BC, 27 BC and 25 BC. The first and third were called off due to revolts elsewhere in the empire, the second because the Britons seemed ready to come to terms. Strabo's Geography, written during this period, says that Britain paid more in customs and duties than could be raised by taxation if the island were conquered.
By the 40s AD, the political situation in Britain was apparently in some chaos.  Caligula planned a campaign against the Britons in 40, but it never happened. Caligula's preparations made Claudius' invasion possible three years later. For example, Caligula built a lighthouse at Bononia (modern Boulogne-sur-Mer) that provided a model for the one built soon after at Dover.