There were once several altars in this retro-choir; under the east window on the south side one to our Lady of the Four Tapers, with an aumbry and triple-arched piscina in the south wall. This has been restored; the upper part is entirely new. On the north side in a corresponding position was an altar dedicated to St. Michael; while altars dedicated to St. Edmund, King and Martyr, and to St. Peter stood to the west of the two pillars, respectively on the north and south sides; and another altar to St. Amphibalus stood to the west of his shrine in the centre. It may here be noted that the east wall of the original Norman apse extended as far as the centre of the retro-choir.
The north aisle of the Saint's Chapel is divided from the retro-choir by a glazed oak screen with a door in it, frequently kept locked. Just to the west of this is the pedestal of the shrine of St. Amphibalus. This, like that of St. Alban's shrine, was broken up into many fragments after the dissolution of the monastery. The fragments were built into sundry walls, but many of them were discovered when the walls blocking up the arches at the east end of the Saint's Chapel were removed; they were put together as far as possible, but as the east and north sides are missing, the position the pedestal now occupies is not an unfitting one, as these sides are hidden (see illustration, p. [65]). The letters R.W. may be seen on it. These are the initials of Ralph Whitechurch, sacrist, at whose cost the pedestal was built in the second half of the fourteenth century. Opposite this we see the back of the watching loft (see illustration, p. [66]) erected for the monk who kept watch and ward over the martyr's shrine; further to the west is a doorway into the Saint's Chapel, and still further west the back of Ramryge's chantry. Beyond this is the north entrance into the presbytery, over which is a painting of the Lord's Supper, generally attributed to Sir James Thornhill and given to the church about two centuries ago; at one time it hung over the high altar. There is also a painting of Offa, probably fifteenth-century work, to be seen in this aisle. The two doors removed by Lord Grimthorpe from the central doorway of the west front have been set up against the west end of the walls of this aisle (see illustration).