It likely had nothing to do with gaining more land to add to the Roman Empire. Instead, Claudius was under intense pressure as a new emperor. His predecessor, the mad and very bad Caligula, had made an absolute mess of things and Claudius needed a quick win to show everyone that he had what it took to be an awesome Emperor. What better way to do that than a military victory which would make everyone proud to be Roman?
Even better for Claudius, if he successfully invaded Britain then he would have achieved a feat that even the great Julius Caesar had failed to do. If Claudius messed the invasion up though… well, his time as Emperor would soon be over!
The conquest of Britain was cause for multiple Triumphs, construction works, and festivals, however it is imperative to understand what factors caused an island of the coast of Gaul to be held in such high regard. Why is it that the Romans wanted to conquer Britain so badly?
To Claudius, and many of the emperors before him, Britain was the ultimate trophy for their personal gloria. To have that gloria announced through the whole empire, to let other rulers of distant lands know that the Emperor of Rome had done the impossible and conquered Britain, to have Britticanicus added to their name would be their hallmark and would certainly set their place in history. For it was this militaristic ideology of Rome that created such an expectation of its rulers. That in order to have a place among the old kings and emperors, you must have had been victorious in a large battle or conquered a great land.
Besides gloria for Rome though, Britain also offered a great reputation to its would-be conquerer, for its known history among the Romans. From reading his Commentaries many Romans were aware of Julius Caesar’s difficulties in Britain. Being the one land he could not conquer, to obtain victory over Britain was to do what Caesar could not himself. To be “first” into Britain was also a prestige of its own. As seen in Caesar’s Commentaries and Tacitus in Agricola, there became the odd tradition among Roman rulers to each have his own departure from tradition. To be the first Emperor to conquer Britain was an accomplishment of this.
Furthermore, The Romans were always curious to explore the unknown. Having only Caesar’s writings and interactions with refugees, Britain was mostly a very unknown and undocumented land before Claudius’s conquest. Roman rulers may have wanted reputation and glory, but scholars and academics were interested in discovering more about Britain and its people. What were the Britons like? How did they live? What did Britain look like?
Without surprise, an interest in potential wealth was another key factor in the desire to conquer Britain. To the emperors, Rome was thought to have had vast unknown riches and wealth, to be taken as the Romans pleased. It was thought this without fact and so Britain, to many Romans, was a sort of “El Dorado”. During Caesar’s attempted conquest, that hope vanished temporarily, only to have invasion reconsidered by both Augustus and Tiberius for a sole desire of wealth.
Finally, we understand Rome’s desire to conquest Britain as a part of the Roman relationship between the empire and the ocean. For ocean to the Romans was the physical boundary of the world. The empire could only stretch this far. It had limited Alexander in his conquest of the world and it would limit the Roman empire too. However, Britain proved a Roman triumph over this concept. Britain was in the ocean and beyond it, so therefor the conquest of Britain would be the conquest of the ocean itself. It proved that the empire was not limited by water and inspired the hope that Rome would continue to expand outward for the rest of its days.