The development, by means of great additions and alterations, of the present eastern arm and its magnificent crypt from the earlier and smaller Norman structures was probably taken in hand about 1190. The new work seems to have been begun from the east and continued westwards. It was at first perhaps roofed temporarily with wood, and only vaulted later. It may have been far enough advanced to allow of William of Perth's burial, directly after his death in 1201, in the north choir transept (still called by his name), where his tomb and shrine were afterwards so much resorted to. On the other hand, his body may have been laid in the north choir aisle until the new transept was ready to receive it. This was probably not the case however; it certainly was not, if the conjecture be correct, that 1195 is the approximate date of the removal of the eastern half of the Norman undercroft and of the portion of the presbytery above it, and that a little work in the choir aisles had been done even earlier. Other authorities, though, incline to the opinion that the part of the Norman presbytery which projected into the new work was not removed before it was almost completely inclosed. This would put off its demolition till later. The "whole choir" was, we read, rebuilt by William de Hoo, the sacrist, with the offerings at St. William's tomb. The word "choir" must here, of course, be used in its more restricted sense, meaning the choir proper, as distinct from its transept and the presbytery. Even then to say absolutely that he rebuilt it is to go too far, for the walls dividing it from its aisles are still in the main of Norman construction, though they have Early English facings and decorations, and additions of this later period to their upper parts. The original intention of the architect had apparently been to change into arcades these solid walls, but, if so, he abandoned it. When the work on the choir walls was finished, some re-modelling of its aisles was soon carried out, buttresses being built within them to withstand the thrust of the new vaulting of the central part. In William de Hoo's work at this time we must include the arches across the western ends of the choir aisles, with the one bay of the transept clerestory over the northern of them, and possibly also the choir arch, with the piers that carry it. It seems, however, that these piers were only finally freed from the Norman nave arcade, and completed, as we now have them, to be the eastern pair of supports to the central tower, by Richard de Eastgate about twenty years later. It is recorded that the new work had been roofed and leaded by the sacrist Radulfus de Ros and the prior Helias. The new choir was first used in 1227, when the monks made their solemn entry into it, and the works, that have been described above, must have been finished at that date. Some fittings, probably originally inserted at this early period, still remain, viz., the eastern side of the pulpitum and some