The keep is constructed of exceedingly rude rubble masonry. Upon two parts of its face are nine narrow and shallow pilaster strips: three towards the barbican, and six between the inner gate and the forebuilding. The keep wall has a rude plinth, with no set-off or string. It is evident that this, as at York, and in other shell-keeps, was lined by lodgings, having an upper floor, placed all round against the wall with an open court in the centre. These were probably of timber. In the part of the keep towards the barbican is a breach about 40 feet broad down to the level of the inner floor. It is said that this part of the wall was partially broken down during General Massey’s attack, and was afterwards enlarged to its present condition, as at Kenilworth, rather as a matter of favour, to render the castle untenable without injuring it as a dwelling. Had the keep been blown up as was usual by gunpowder, it would have presented a very different aspect. If the masonry of Berkeley Castle were to be removed, as at Kilpeck or Ewias Harold, its remains would show a mound of earth, and attached to three sides of it a platform, the whole encircled with a ditch or scarp. It would, in fact, be a moated mound with an appended platform, of a character very common in England, in the Welsh Marches, and in Normandy, and would resemble such works as Tamworth and Towcester, the dates of which are given in the Anglo-Saxon Chronicle. The inference is, therefore, that Berkeley was the seat of an English lord, probably from the ninth century. Had the fortress been an original Norman work, it is scarcely probable that a shell would have been the form of keep selected, or that, having been so selected, its lower 22 feet would have been filled up with earth. Evidently the Norman builder, finding a moated mound of no great height, but of considerable breadth, built his shell round it, as at Pontefract, as a revetment wall, and upon this, when clear of the top of the mound, raised his curtain. At a lower level, along the scarp of the existing ditch, he, or his immediate successor, constructed the walls, which, then as now, contain the whole castle. All the main walls of the castle are either Norman, or rebuilt upon Norman foundations, or very nearly so. Probably the keep was built first and the court enclosed shortly afterwards. Much was done in the Decorated period. The inner wall of the hall, at least, was rebuilt, and it may have been enlarged. The porch was added, the chapel much altered, and the domestic buildings possibly gutted and recast. Henry VII., when in possession, seems to have made some inconsiderable alterations, and others have been added since.