The last two recorded events in Abbot William’s reign consisted of his supervising the election of John R. to the abbacy of St Radegund's, Kent in 1345 and witnessing, along with canon I. de W., the provision made for the retiring abbot, and his lending the king 50s. toward the war in France, to be repaid in November 1348. The king begged the loan of four sacks of wool to be delivered in London on 30th September 1347.
The double Purbeck marble slab in the middle of the site museum on the site of the Chapter House, which in 1878 bore a cross fleury, is thought to cover the graves of Abbot William and abbot number 13.
Abbot number 13: Roger de Kyrketon
Abbot Roger ruled for three years and 20 weeks from 1354 to 1358. The years appear to have passed without event of note. Kirk Hallam church was served by canon Hugh de Claypoll from 1354 till his resignation in 1360.
Abbot number 14: William de Boney
Abbot William ruled for 42 years and 14 weeks from 1358 to 1400 and “re-edified many ruinous tenements". His was the longest reign of any abbot at St Mary’s.
During this period there was considerable acquisition of land and rents: in 1364 the king granted him a licence to acquire £20 of land and rent annually on condition that the abbey prayed for him for ever; in 1365 the abbey acquired land in Derby, to the value of 60s. annually, for the lodging of victuals and other necessities; in 1375 the abbey acquired more land in Derby to the annual value of 10s., and in 1382 it was land in Trowell, Lambercote and Radcliffe; in 1383 the abbey acquired land in Stanton, Alvaston, Elvaston, Thulston, Bolton, Stanley, Kirk Hallam and Spondon to the yearly value of 50s.; in 1385 Abbot William was licensed by Lord Zouche (William la Zouche of Harringworth) to appropriate the rectory of Ilkeston (as a result of this, the abbey granted the dean and chapter of Lichfield 6/8d. per annum because they had laid claim to the rectory for many years. This was still being paid in 1535); and in June 1392 the abbey acquired land (five messuages, 100 acres of land and 13 acres of meadow) in Elvaston, Stanley, Thulston and Alvaston.
These endowments enabled the abbey to carry out its ministry of hospitality and healing. In one abbey charter, 14 bovates were granted for the sustenance of three canons; sustenance did not mean full maintenance.of a canon, but rather a chantry endowment for the performance of masses.
On 25th October 1361 Bishop Roger de Stretton stayed at St Mary’s Abbey. The abbey was now in a position to make loans, and in 1379 it lent Richard II five marks as a war loan.