It has been noticed that the architecture is plainer here than in contemporary examples in France, but lighter, probably because intended to have a wooden roof. From the west wall the Norman work extends as far as the sixth bay of the nave arcades, the seventh and eighth bays being, with part of the sixth, the work of Early Decorated builders. The half piers at the west wall and the Norman piers facing each other in the nave arcades form pairs, but each pair differs from the rest. The pier capitals are flat, with scalloped ornaments. The semi-cylindrical shafts starting from them are now stopped by the plain string course that divides this from the next story. If they were continued further they would only emphasize the irregular placing of the Perpendicular clerestory windows, but they probably rose originally to bear the main timbers of the roof. The arches of the lowest story are semicircular, of course, and are in two orders. Both orders were, it is believed, plain throughout, in early Norman times, and they still continue to be so on the aisle side of the south arcade. The inner order is still plain everywhere, but the outer has zigzag and other mouldings. In each bay of the triforium, the tympanum is filled with an elaborate diaper around a central ornament. This decoration varies in every bay, and is thought to be a later insertion. It is noteworthy that the triforium arcades open into the aisles as well as into the nave, an unusual arrangement, which seems, however, here to be part of the design of the twelfth century. This opinion is supported by the existence of the narrow gallery, now blocked up, in the thickness of the wall. The early Norman triforium arcades seem to have been removed by the architects of the following period, and replaced in the present form. The aisles were perhaps originally vaulted; the flat pilasters of their outer walls might then have been built as vaulting shafts. If such was the case, the vaulting must have been found too heavy for the walls, and a wooden roof have been therefore adopted in its stead. The easternmost bay of the triforium, on each side, is apparently later Norman like the rest, but is really the work of masons of the Decorated period. It had been demolished in connection with the rebuilding of the nave, in progress at that time but abandoned when only two bays were finished. It was then found that the best way to make the junction of the styles good would be to restore the old work as accurately as possible. This was well done, but differences of material and in methods of working save us from being deceived.