Abbot Michael de Mentmore (1335-49) completed the restoration of the S. aisle and repaired the _Cloister_. His successor, Thomas de la Mere, paved the W. floor, and no doubt minor restorations were almost continually in progress during the latter half of the fourteenth century; but a new chapter in the story of the Abbey commenced when John de Wheathampsted became abbot (1420-40 and 1451-64). This celebrated man, during the two periods of his abbacy, hardly rested in his efforts to beautify the Abbey. It is stated in a Cottonian MS. that this abbot constructed a little chapel near the shrine of St. Alban; this was perhaps the _Watching Loft_ (N. of _Saint's Chapel_) in which the keeper of the holy shrine and relics (Custos Feretri) spent much of his time. John de Wheathampsted also built the tomb of Humphrey, Duke of Gloucester (d. 1447), on the side of the chapel opposite the _Watching Loft_ (a few steps lead down to the coffin); prepared his own tomb W. from that of the duke; built the great Perp. window over the W. porches, now replaced by one Dec. in design, and the nine N. windows of _Nave_ and _Ante-Choir_; and was probably responsible for the paintings discovered on the choir ceiling, and for many of the embellishments of the _Lady-chapel_. Perhaps, however, his fame chiefly rests on the _High Altar Screen_, which he designed, but which was erected by the thirty-sixth abbot, William Wallingford (1476-84). There were apparently few important features added to the Abbey, and but little restoration effected during the rule of the last four abbots (1492-1539). A few brief paragraphs concerning its modern restorations and present appearance must now be added. Those modern restorations date largely from the middle of last century. Its condition, internally and externally, was at that time certainly discreditable to everybody concerned in its welfare. In 1856 a National Committee placed the matter in the hands of Sir Gilbert Scott, under whose direction the building was in part restored; but public funds presently failed and in 1879 the direction of the workers was undertaken by one who had at once the inclination and the funds necessary to its completion--Lord Grimthorpe. The _Abbey_, from the W. porches to the E. end of the _Lady-chapel_ and the _Chapel of Transfiguration_, measures inside 520 feet, outside 550 feet; the entire _transept_ length from N. to S., on the floor, 177 feet; the _nave_, the longest Gothic one in the world, 292 feet x 75 feet 4 inches; the _Lady-chapel_, 57 feet x 24 feet; the great _Screens_ are rather less than 170 feet apart; the height of the _tower_ is 144 feet. Visitors will find some slight discrepancies as to measurements in the several guides which have been compiled; but the foregoing figures will assist them to realise the vast dimensions of the building. Its area is approximately 40,000 square feet. Of special interest are:--