Graham Webster 
The Roman Invasion of Britain [PDF ebook] 

First Published in 2004. The span of time, when most of Britain was under Roman influence, stretched from 55 BC to c. AD 500, when control had passed into the hands of Germanic peoples, many of whom had been living here already for over a century as troops or allies of the Roman army. Five and a half centuries is a considerable portion of our national history. If one counts back from today, it brings one to about 1440, at the end of the Middle Ages, a period totally remote from our present world. This revised edition takes into account aerial archaeology and major rescue excavations.