A Burh is an Old English name for a fortified town or other defended site, sometimes centred upon a hill fort though always intended as a place of permanent settlement, its origin was in military defence; "it represented only a stage, though a vitally important one, in the evolution of the medieval English borough and of the medieval town", H. R. Loyn asserted. The boundaries of ancient burhs can often still be traced to modern urban borough limits. Most of these were founded by Alfred the Great in a consciously planned policy that was continued under his son Edward the Elder and his daughter, Æthelflæd, "Lady of the Mercians" and her husband Æthelred, Ealdorman of Mercia; the Mercian Register tells of the building of ten burhs by Æthelflæd, some as important as Tamworth and Stafford, others now unidentifiable. Some were based on pre-existing Roman structures, some newly built, though some may have been built later. Æthelstan granted these burhs the right to mint coinage, and in the tenth and eleventh centuries the firm rule was that no coin was to be struck outside a burh.
A 10th century document called the Burghal Hidage cites 30 burhs in Wessex and three in Mercia (then under the domination of the West Saxon kings), built to defend the region against Viking raids.
Only eight of the burhs achieved municipal status in the Middle Age: 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 9,000 feet of bank would have taken more than 120,000 man hours. Burh towns also usually had regular street layouts, some of which are also preserved.