Of the building carried out at this time, except the screen of the chantry chapel and some portions of the restored cloister, but little remains, and all the evidences which might have enabled us to determine how far the east wall was a restoration, or an entirely new work, were swept away when the apse was rebuilt. That this east wall was not merely a reredos is shown by the fact that the upper part rose clear of the aisles, and was pierced by two large traceried windows in the same position as the Georgian windows which lighted the church in the last century, and it is quite possible that it was only a restoration of an earlier wall, which had been built across the apse so as to make it conform to the Austin Canon rule. The screen of the chantry chapel, the two eastern bays of which have been destroyed, but which is shown complete in our illustration (fig. 5), may have been continued across the east wall, and formed the reredos itself, but all traces of this were effaced in subsequent alterations. [Illustration: FIG. 5--SCREEN OF ROGER DE WALDEN'S CHANTRY, AND RAHERE'S MONUMENT.] One alteration was made in the choir which very much affected the proportions of the building between the date of its first building and the erection of Rahere's monument. Perhaps because the ground outside the church had become raised by the building operations, which had gone on around it, and the drainage of the interior had become defective, or for some other reason, the floor over all the eastern part was filled in for a depth of nearly three feet, dwarfing considerably the Norman arcades, and burying the bases of the columns; and it was upon this altered level the screen of Bishop Roger de Walden's chantry was built. Having undergone such extensive repairs the priory received no further alterations until, after another hundred years, William Bolton became prior in 1506. It has been asserted, on what seem very insufficient grounds, that Bolton was the architect of Henry VII.'s Chapel at Westminster; but although this is very improbable, he was associated with those who were engaged on the work, and seems himself to have been disposed to architectural display. He has been credited with very large alterations to the conventual buildings, and the erection of a tower over the crossing; but nearly all traces of his work have disappeared, except a doorway in the south aisle, and the beautiful window in the triforium, overlooking the choir, which is always, known as "Prior Bolton's window," and is distinguished by his rebus, a bolt in a tun, in the centre lower panel, as is shown in the illustration (fig. 6). Bolton's successor, Robert Fuller, was the last of the priors, and with him is ushered in the era of dissolution and decay, when-- "The ire of a despotic King Rides forth upon destruction's wing."