The ancient boroughs were a historic unit of lower-tier local government in England and Wales. The ancient boroughs covered only important towns and were established by charters granted at different times by the monarchy. Their history is largely concerned with the origin of such towns and how they gained the right of self-government. Ancient boroughs were reformed by the Municipal Corporations Act 1835, which introduced directly elected corporations and allowed the incorporation of new industrial towns. Municipal boroughs ceased to be used for the purposes of local government in 1974, with borough status retained as an honorific title granted by the Crown. Anglo-Saxon burhs Throughout Britain, the effect of the Germanic invasions which completed the decline of the Roman Empire was to destroy the Roman municipal organisation. After the Anglo-Saxon settlement of Britain, the ruins of Roman colonies and camps were used by the early English to form tribal strongholds. Despite their location, burhs on the sites of Roman colonies show no continuity with Roman municipal organisation, and instead resemble the parallel revival of urban centres in continental Europe. The resettlement of the Roman Durovernum under the name "burh of the men of Kent," Cant-wara-byrig or Canterbury, illustrates this point. The burh of the men of West Kent was Hrofesceaster (Durobrivae), Rochester, and many other ceasters mark the existence of a Roman camp occupied by an early English burh. The tribal burh was protected by an earthen wall, and a general obligation to build and maintain burhs at the royal command was enforced by Anglo-Saxon law. Offences in disturbance of the peace of the burh were punished by higher fines than breaches of the peace of the hām or ordinary dwelling. However, neither in the early English language nor in the contemporary Latin was there any fixed usage differentiating the various words descriptive of the several forms of human settlement, and the fortified communal refuges cannot accordingly be clearly distinguished from villages or the strongholds of individuals by any purely nomenclative test. Danish invasions At the end of the 9th century and beginning of the 10th century there is evidence of a systematic "timbering" of new burhs, with the object of providing strongholds for the defence of Wessex against the Danes, and it appears that the surrounding districts were charged with their maintenance. It is not until after the Danish invasions that it becomes easier to draw a distinction between