been at hand, and the weapons over their head.'[27] No improvement in the condition of houses in London appears to have taken place until long after the Conquest, and the low huts, closely packed together, which filled the streets during the Saxon period, were continued well into the thirteenth century. These houses were wholly built of wood, and thatched with straw, or reeds. All mediæval cities were fatally liable to destruction by fire, but London appears to have been specially unfortunate in this respect. In the first year of the reign of Stephen a destructive fire spread from London Bridge to the Church of St. Clement Danes, destroying St. Paul's in the way. This fire caused some improvements in building, but special regulations were required, and one of the early works undertaken by the newly established 'Commune' was the drawing up, in 1189, of the famous Assize of Building, known by the name of the first Mayor as Fitz-Ailwyne's Assize. In this document the following statement was made: 'Many citizens, to avoid such danger, built according to their means, on their ground, a stone house covered and protected by thick tiles against the fury of fire, whereby it often happened that when a fire arose in the city and burnt many edifices, and had reached such a house, not being able to injure it, it there became extinguished, so that many neighbours' houses were wholly saved from fire by that house.'[28] Various privileges were conceded to those who built in stone, and these privileges are detailed in the Assize of 1189. No provision, however, was made as to the material to be used in roofing tenements. This Assize, which has been described as the earliest English Building Act, is of the greatest value to us from an historical point of view, and much attention is paid to it in Hudson Turner's _Domestic Architecture_, where a translation of the Assize is printed. Turner points out that it is evident from this specimen of early civic legislation that although citizens might, if it so pleased them, construct their houses entirely of stone, yet they were not absolutely required to do more than erect party walls 16 feet in height, the materials of the structure built on such walls being left entirely to individual choice, and there can be no doubt that in the generality of houses it was of wood. This assumption is justified by the fact that, in deeds of a much later period, houses constructed wholly of stone are frequently named as boundaries, without any further or more special description than that such was the substance of which they were built. Turner adds that it is obvious such a description would have been vague and insufficient in a district where houses were generally raised in stone, and he therefore supposes that the Assize of 1189 had no more direct effect than in regulating the method of constructing party walls, and then only in cases where individuals were willing to build in stone.[29]