The Presbytery, Ambulatory, or retro-choir, is the space between the back of the reredos and the entrance to the lady-chapel. The design in detail of these two bays is very different in character from the three in the choir, which are like those in the nave. The two piers of Purbeck marble are circular, and about them are grouped four detached shafts of the same material. They are united only at the base and by the abacus above the capitals, which are beautifully carved (see page [16]). The main arches in the two bays are not pointed,
but round, like those in the nave and choir; but, unlike the latter, they have deeply cut mouldings in three orders. The triforium arcade above, on the north and south sides, has moulded and carved details of a similar character. Some of the beautifully carved figure-work still remains in the spandrels between the subsidiary pointed arches. But the most beautiful piece of design in all this work is in the arches of the triforium passage across the east wall, above the entrance to the lady-chapel.
It should be noticed that the sub-arches in the triforium here are pointed, not round, as in the case of those in the same position westward of this portion. And the support to these arches in the centre, is a group of shafts instead of only one column. The clerestory, however, offers a greater contrast to the earlier work in that the central arch, as well as the side ones, is lifted up much higher, the detached columns being lengthened to obtain the alteration. Each arch also, at this level, is now pointed.
S. Richard's shrine occupied the bay in the presbytery immediately behind the High Altar. It stood upon a platform which was approached on its eastern side by steps, and was enclosed by iron grilles. The platform was removed at the time of the general restoration in 1861-1867, and upon it used to stand also the tombs of Bishop Day and Bishop Christopherson or Curteys.
The Lady-Chapel, as its walls and vaulting clearly show, was once completely decorated with designs in colour. The windows now are the only parts that indicate an attempt to renew this portion of its earlier condition. The new reredos is of alabaster, and was designed by Messrs Carpenter & Ingelow.
The North Choir Aisle contains some monuments which are referred to separately. The now unused chapel at its eastern end was dedicated to S. Catharine.
The Library is approached through a doorway in this aisle. There is a chamber above in which was the library of pre-Reformation days. The present library formed the chapel of S. John the Baptist and S. Edmund the King (13) until it became the chancel of the parish church of S. Peter the Great, the north transept being used as its nave. Part of the vaulting in it is unlike any other in the building, having the chevron or zigzag ornament cut on the side of the mouldings of the ribs (see page [98]).