The Romans arrived in Britain, led by the famous conqueror Julius Caesar, in 55 B.C. At the beginning of their occupation they weren't very interested in this land and they soon abandoned it. Only under the reign of Emperor Claudius, from 43 A.D. the Romans began to settle Britain permanently.
We have to consider this period of roman occupation as a moment of wellness and internal political stability because there was a great demographic increase (the population raised up to 5 million people) and no other populations dared to attack Britain.
The roman didn't succeed in conquering all Britain: in the north of the island they were stopped by the Scots and Pichts, also named Caledonians by the Romans, they were fierce warriors and refused to be colonized and eventually Emperor Hadrian in 122 A.D. decided to build a wall to keep these northern raiders out of roman Britain. The construction of the wall was a vast undertaking because it's long 73 miles and it's a complex structure composed of forts and turrets. On the north side there was a ditch and in the south side of the Wall lay the vallum which is a flat bottomed ditch with a narrow ledge and then a turf mound on either side.
The roman civilization made the population lifestyle better because they introduced many technological innovations such as drainage system, running water in towns, water supply and heating devices in the houses. However these modernizations were only introduced in the wealthy's houses and not in the wooden huts where the poorest part of the population lived.
Romans built a large nets of roads and bridges to connect town centers in fact they were very good engineers and even today their constructions are in use.
They also built baths and bathing establishment. One of the finest example of this roman type of architecture is the city of Bath which flourished between the first and the fifth century A.D. It was built around the only natural hot spring of water in Britain. The were called Aquae sulis, the remains are remarkably complete.
Under the late roman empire Christianity was first introduced into parts of Celtic Britain. A Latin cryptogram was found at cirencester and it dates back to the second or third century a.d. It consists in a secret sign that the Christians used to communicate with each other in times of persecution.