was to be struck outside a burh. A tenth-century document, now known as the Burghal Hidage and so named by Frederic William Maitland in 1897, cites thirty burhs in Wessex and three in Mercia. At the time, Mercia was ruled by the West Saxon kings. These burhs were all built to defend the region against Viking raids. Only eight of the burhs achieved municipal status in the Middle Ages: Chester, Bridgnorth, Tamworth, Stafford, Hertford, Warwick, Buckingham and Maldon. The largest were at Winchester, Wallingford and Warwick, whilst Wallingford and Wareham are the best-preserved examples, with substantial ditches and banks still visible. It has been estimated that construction of Wallingford's of bank would have taken more than 120,000 man hours. Burh towns also usually had regular street layouts, some of which are still preserved. Burhs are widely thought to have been the origins of urban life in England. In most cases, Alfred's rebuilding of a burh did not cause any change of name, as the sites chosen had already been some sort of fortified structure. Construction The burhs were made in a variety of different ways, depending on materials available locally, and the size of the settlement or area it was intended to defend. Frequently, a burh was built on the site of pre-existing fortifications. Sometimes, old Roman walls were simply repaired, as in towns such as Winchester, Exeter, York, Burgh Castle, Portchester and Dover. At other times, they would build on the site of old Iron Age forts, such as Dover, utilising the old ditches and ramparts. However, many of the burhs were entirely new fortified sites, built on strategic sites on the coast, near ports or overlooking roads and trade routes. Substantial new towns were built on flat land with a rectangular layout, at for example Oxford, Wallingford, Cricklade and Wareham. Traditionally, burhs were constructed first with a massive series of banks fronted by a ditch. The bank was typically timber faced and timber revetted. This was topped by a wooden palisade of stakes, up to high, with a walkway. At towns such as Tamworth, the ramparts would decay and push outwards over time, meaning that the ditch and bank would deteriorate. To solve this, the banks were faced with stone, thus further reinforcing the defences and improving their life span. Purpose The purpose was primarily to provide defence for a port or town, and the surrounding farms, villages