Throughout western Europe, 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.
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 the burhs that served as military strongholds for national defence and the royal vills which served no such purpose. Some of the royal vills eventually entered the class of boroughs, but by another route, and for the present the private stronghold and the royal dwelling may be neglected. It was the public stronghold and the administrative centre of a dependent district which was the source of the main features peculiar to the borough. Many causes tended to create peculiar conditions in the boroughs built for national defence. They were placed where artificial defence was most needed, at the junction of roads, in the plains, on the rivers, at the centres naturally marked out for trade, seldom where hills or marshes formed a sufficient natural defence. Typically, the fortification of a burh consisted of earth ramparts faced with timber. Palisades were sometimes used.
The concept of a network of burhs as a defence in depth is usually attributed to Alfred.
The solution that Alfred devised for this apparently intractable predicament was nothing short of a revolution and that revolution began now in the 880s. If the Vikings could attack anywhere at any time, then the West Saxons had to be able to defend everywhere all the time. To make this possible Alfred ordered the construction of a network of defended centres across his kingdom, some built on refortified Roman and Iron Age sites, some built completely from scratch. These burhs were to be distributed so that no West Saxon was more than twenty or so miles – a day's march – from one of them.
This network is described in a manuscript document which has survived in later iterations, named by scholars the Burghal Hidage, which lists thirty three burhs in Wessex and English Mercia. Most of these survived into the post Norman Conquest era and are the core of later Parliamentary Boroughs and municipal corporations.
Following the successful reconquest from the Vikings by Alfred's descendants Edward and Æthelstan, the latter made a series of reforms in law, the Codes issued at the Council of Grately, which gave additional impetus to the urban development of the burhs which hitherto had been mainly forts. The burhs drew commerce by every channel; the camp and the palace, the administrative centre, the ecclesiastical centre (for the mother-church of the state was placed in its chief burh), all looked to the market for their maintenance. The burh was provided by law with a mint and royal moneyers and exchangers, with an authorised scale for weights and measures. Mercantile transactions in the burhs or ports, as they were called when their commercial rather than their military importance was accentuated, were placed by law under special legal privileges in order no doubt to secure the king's hold upon his toll. Over the burh or port was set a reeve, a royal officer answerable to the king for his dues from the burh, his rents for lands and houses, his customs on commerce, his share of the profits from judicial fines.
Legal and administrative roles
Edgar, King of England 959 to 975
At least from the 10th century the burh had a moot or court, the relation of which to the other courts is matter of speculation. A law of Edgar, about 960, required that it should meet three times a year, these being in all likelihood assemblies at which attendance was compulsory on all tenants of the burghal district, when pleas concerning life and liberty and land were held, and men were compelled to find pledges answerable for their good conduct. At these great meetings the borough reeve (gerefa) presided, declaring the law and guiding the judgments given by the suitors of the court. The reeve was supported by a group of assistants, called in Devon the witan, in the boroughs of the Danelaw by a group of (generally twelve) " lawmen," in other towns probably by a group of aldermen, senior burgesses, with military and police authority, whose office was in some cases hereditary. These persons assisted the reeve at the great meetings of the full court, and sat with him as judges at the subordinate meetings which were held to settle the unfinished cases and minor causes. There was no compulsion on those not specially summoned to attend these extra meetings. At these subordinate jurisdictional assemblies, held in public, and acting by the same authority as the annual gathering of all the burh-wara, other business concerning borough administration was decided, at least in later days, and it is to these assemblies that the origin of the town council may in many cases be ascribed.
In the larger towns the division into wards, with a separate police system, can be traced at an early time, appearing as a unit of military organisation, answerable for the defence of a gate of the town. The police system of London is described in detail in a record of 930–940. Here the free people were grouped in associations of ten, each under the superintendence of a headman. The bishops and reeves who belonged to the "court of London" appear as the directors of the system, and in them we may see the aldermen of the wards of a later time. The use of the word bertha for ward at Canterbury, and the fact that the London wardmoot at a later time was used for the frankpledge system as well as for the organisation of the muster, point to a connexion between the military and the police systems in the towns.
In charters of the Anglo-Saxon period a haw, or enclosed area within a burh, was often conveyed by charter as if it were an apanage of the lands in the neighbourhood with which it was conveyed; the Norman settlers who succeeded to lands in the county succeeded therewith to houses in the burhs, for a close association existed between the thegns of the shire and the shirestow, an association partly perhaps of duty and also of privilege. The king granted borough haws as places of refuge in Kent, and in London he gave them with commercial privileges to his bishops. What has been called the heterogeneous tenure of the shirestow, one of the most conspicuous characteristics of that particular type of borough, was further increased by the liberty which some burgesses enjoyed to "commend" themselves to a lord of their own choosing, promising to that lord suit and service and perhaps rent in return for protection. Over these burgesses the lords could claim jurisdictional rights, and these were in some cases increased by royal grants of special rights within certain sokes. The great boroughs were honeycombed with sokes, or areas of seignorial jurisdiction, within which the royal reeve's authority was greatly restricted while that of the lord's reeve took precedence. Even the haws, being "burhs" or strongholds within a stronghold, enjoyed a local "peace" which protected from official intrusion.
Besides heterogeneity of tenure and jurisdiction in the borough, there was also heterogeneity of status; there were burh-thegns and cnihts, mercatores, burgesses of various kinds, the three groups representing perhaps military, commercial and agricultural elements. The burh generally shows signs of having been originally a village settlement, surrounded by open fields, of which the borough boundary before 1835 will suggest the outline. This area was as a rule eventually the area of borough jurisdiction. There is some evidence pointing to the fact that the restriction of the borough authority to this area is not ancient, but due to the Norman settlement.