After a lapse of two hundred years, it is not unlikely that the building had fallen somewhat into a state of dilapidation and for that reason, as well, perhaps, from a desire for improvement and display, large works of alteration and rebuilding were undertaken at the beginning of the fifteenth century. Prior John Walford, of whom little is known, except that he was summoned to a convocation at Oxford in 1407, is credited with the work, which embraced the new east wall to the choir, and perhaps a reredos, the Lady Chapel and chapels, on the north side of the north ambulatory, and the rebuilding of the east walk of the cloisters with rooms above. But although Prior John may have been the agent for carrying out all these works, the initiative was probably due to Roger de Walden, afterwards Bishop of London. This man, who had a most remarkable career, was in some way closely associated with St. Bartholomew's, for his stepmother resided in its vicinity, and he had a brother John, a man of considerable wealth, who is described as an esquire of St. Bartholomew, Smithfield. During the reign of Richard II., Roger de Walden held high and lucrative ecclesiastical appointments, and in 1395 became Dean of York and Treasurer of England, and when Archbishop Arundel was banished from the realm in 1397 for his share in the conspiracy of his brother, Roger was advanced to the See of Canterbury. After the downfall of Richard, Arundel returned to England, and Roger was ousted from his seat; but strange though it may appear, the Archbishop bore him so little ill-will for his usurpation that he induced Henry IV., though with some difficulty, to agree to his nomination to the Bishopric of London at the next voidance of the See. As Bishop of London, he died in 1406, and though he lay in state in his chantry chapel at St. Bartholomew's, it is believed that he was actually buried in St. Paul's Cathedral. [Illustration: FIG. 4--EAST BAY OF SOUTH AISLE OF NAVE.] It was during his years of prosperity, and before he had anticipated the honours to which he afterwards succeeded, that he built his chantry chapel in the church with which his early youth was doubtless associated, and tradition, to some extent supported by both architectural and heraldic evidence, has identified the screen in which Rahere's monument is encased as a portion of that chapel. The beautiful canopies and tracery, the character of the carving of the effigy and its attendant figures, and the arms of England emblazoned on one of the shields, all point to a date supporting the tradition, whilst the arms, which seem undoubtedly to be Walden's, displayed on the fourth shield make it improbable that the work can be assigned to any other person.