The doorway beneath the monument opens on the staircase to the south triforium.
The Choir, now restored as nearly as possible to its original state, consists of five bays on each side, with an apsidal termination of five arches, distinguished from the others (mainly semicircular) by their "stilted" form and much narrower span, which, in fact, measures no more than the diameter of the intervening columns, and gives an appearance of extra massiveness to the east end of the church. All the arches display some approximation to the "horseshoe," in a slight inward inclination on either side towards the capitals on which they rest; but the shape is very definitely assumed in each of those immediately contiguous to the transverse curve. These are of the genuine "horseshoe" pattern characteristic of Arabian or Moorish buildings; and their exact similarity in detail, with their position facing one another at each extremity of the apse, would seem to indicate a structural necessity, or deliberate intention in the design, which, neither here nor elsewhere in the arcading, is to be attributed to any subsidence, or imperfect workmanship, sometimes held to account for the deflection as a mere accident.
The character of these arches, with the slightly domical vaults noticeable in the adjacent aisles, has led some persons to detect an Oriental influence in the building—possibly traceable to the visitors from Byzantium whom the founder is said to have consulted while it was in course of erection—though it is argued to the contrary that these features are sufficiently accounted for by the general tendency of Anglo-Norman architecture at the time, as illustrated elsewhere.
The arcading throughout rests on massive piers and circular columns, with square bases and abaci (incised at the angles) and low cushioned capitals, ornamented with a simple scallop. Above the arches, on the choir side, there is a billet moulding, which is considered unique in that, instead of forming a separate decoration to each arch, it is carried along horizontally above the abaci on either side in a continuous line of ornament.
The Triforium consists of a series of rounded arches, the piers from which they spring being placed directly above those of the main arcade. Each of the side bays is divided into four compartments by small columns, above which the tympanum of the enclosing arch is occupied by a blank wall. The sequence is, of course, interrupted by the oriel window in the central bay on the south; and the narrower openings in the apse only admit of a twofold division. There are said to have been originally windows at the back of the triforium-gallery, as at Durham, Peterborough, and other Norman churches of the same period; but the mutilation and rebuilding in the external walls have greatly destroyed the original work.
Prior Bolton's Window was probably inserted about 1530, when the device of a "bolt in tun" was officially authorized for Bolton's arms, on his own choice, as presenting his name in the emblematical form then in vogue. The window is an "oriel" in the Perpendicular style, separated vertically by mullions into three lights in front, with one at each end of the projection, and horizontally by transoms into an upper and lower tier, the former having a trefoil heading to each division. There is a sloping hipped roof to the window, and a broad moulded corbel below it. The well-known rebus is boldly displayed upon the central of the five square panels (all sculptured) which adorn the face of this picturesque chamber (oriolum), probably built as a convenient private pew for the Prior, from which he could survey the whole of the choir and the Founder's tomb. The Tudor doorway, which now opens into the choir vestry at the eastern end of the south wall, has the Bolton rebus in the spandrels of the arch.[3]
The Clerestory.—In his reconstruction here Sir Aston Webb has followed the precedent of the Perpendicular work introduced in the fifteenth century, which, fortunately, had not been seriously injured in the upper part of the side walls. He has accordingly adopted that style in the apse, where the clerestory arcade is entirely new. It displays a series of five windows of two lights each, with traceried headings, and slender columns on the inner and outer plane, sufficient to uphold the arcading without intercepting the light—none too abundant in any part of the church, though it is entirely destitute of stained glass at the present day.