Demography of the United Kingdom - Wikipedia
https://en.wikipedia.org/wiki/Demography_of_the_United_KingdomRoman Britain had an estimated population between 2.8 million and 3 million at the end of the second century AD. At the end of the fourth century, it had an estimated population of 3.6 million, of whom 125,000 consisted of the Roman army and their families and dependents. The urban population of Roman Britain was about 240,000 people at the end of the fourth century. Roman Britain's capital city, Londinium, is estimated to have had a population of about 60,000. Londiniu…