The present choir was commenced at the very beginning of the thirteenth century. Of this choir only the lower portions of the three bays nearest the tower remain above ground, but there is no doubt that the original eastern termination had been removed to make way for the beautiful presbytery which now remains and extends eastward, with its vaulting at the same elevation as that of the choir. This was done probably immediately after the Lady Chapel had been built, or at the same time, and it is supposed that the work proceeded from the east end and the old choir was gradually pulled down, leaving the three western bays standing, and that then the clerestory of these bays was replaced by work in uniformity with that in the new presbytery; at the same time the front half of their pier arches was removed and mouldings given to them corresponding to those in the presbytery, their piers were also slightly altered. In this way the choir and presbytery acquired a uniform appearance, both inside and out; for the portion of the old side aisle on the south is hidden by the sacristry, and that on the north by the chapter-house and vestibule. As has been said, only one of the original Decorated clerestory windows now remain; the others, it may be supposed, were destroyed in the sieges of the Civil War, for they have been replaced with Perpendicular tracery which belongs to a period when this style was only being imitated; it was probably put in at the Restoration. The high altar is now placed between the sixth pair of piers (counting from the west). This is probably the old arrangement, but until the recent restorations the altar was placed in the Lady Chapel: the pier arches of the choir were walled up, and a large screen placed in the eastern tower arch; so that the choir and Lady Chapel were converted into one long aisleless chapel. [Illustration: THE CHOIR, LOOKING EAST.] It is very interesting to note the signs in the choir of the attempt to combine the two styles which, as has been explained, met here. The third piers stand on the line of demarcation between the part retained and the part rebuilt, and consequently carry an Early English arch to the west and a Decorated arch to the east. The Early English column was partially cut away and partially used in the new work, as may be seen on inspection of these piers. It will also be seen that the vaulting in the aisles is much rougher in the old part than in the eastern bays. The plaster used to hide this; but Sir Gilbert Scott caused it to be removed, and is said afterward to have regretted having done so. [Illustration: SOUTH AISLE OF CHOIR, LOOKING EAST.] Another interesting junction between two buildings of different dates is the entrance to the vestibule of the chapter-house. This entrance is in the third bay of the north aisle, and is obviously a combination of doorway and window, as may be seen by comparing the window of the first bay with it.