It was originally an Iron Age hillfort in which the Romans may have constructed a small military station about AD 70. The settlement seems to have become civilian in nature around fifty years later. Most of the buildings discovered so far were of timber construction. They had both tiled and thatched roofs and some had painted plaster internal walls. Only one stone building has been located. The town went into decline during the 3rd century, but expanded after its walled defences were put in place a hundred years later. There were four gates and a cemetery to the south. Occupation seems to have continued until the Roman departure from Britain around 410, but it has been identified as the listed among the 28 cities of Britain by the "History of the Britons" and the invading Saxons had begun occupying the area by the end of the century.