Britannia, that is England and Wales south of Hadrian’s Wall, was occupied by Rome for 450 years, the length of time that has elapsed since the reign of Elizabeth I to the present day. It encompassed the Roman Republic and Empire, the passage from paganism to Christianity and from tribal Celtic barbarism to a colonial, provincial version of Greco-Roman civilisation. When William I was crowned in London in 1066, there were still buildings standing which had been  put up in the Roman period. Conquered in AD 43 by the Emperor Claudius, there were elegant villas dotted around the landscape by AD 130: Londinium had a forum, baths, gladiatorial games and a thriving immigrant population from all over the Empire. The hot springs at Bath had become a noted tourist attraction. There were