During the first half of the 14th century, the priory suffered from financial mismanagement and disputes with the Dutton family, exacerbated by a severe flood in 1331 that reduced the income from the priory's lands. The direct effects of the Black Death are not known, but during the 1350s financial problems continued. These were party mitigated with the selling of the advowson of the church at Ratcliffe-on-Soar. Matters further improved from 1366 with the appointment of Richard Wyche as prior. He was active in the governance of the wider Augustinian order and in political affairs, and in 1391 was involved in raising the priory's status to that of a mitred abbey. A mitred abbey was one in which the abbot was given permission to use pontifical insignia, including the mitre, ring and pontifical staff, and to give the solemn benediction provided a bishop was not present. It was rare for an Augustinian house to be elevated to this status. Out of about 200 Augustinian houses in England and Wales, 28 were abbeys and only seven of these became mitred. The only other mitred abbey in Cheshire was that of St Werburgh in Chester. In 1379 and in 1381 there were 15 canons at Norton and in 1401 there were 16, making it the largest Augustinian community in the northwest of England. By this time the barony of Halton had passed by a series of marriages to the duchy of Lancaster. John of Gaunt, the 1st Duke of Lancaster and 14th Baron of Halton, agreed to be the patron of the newly formed abbey. At this date the church was long; it was the second longest Augustinian church in northwest England, exceeded only by the long church at Carlisle. Towards the end of the 14th century, the abbey acquired a "giant" statue of Saint Christopher. Three wills from members of the Dutton family from this period survive; they are dated 1392, 1442 and 1527, and in each will money was bequeathed to the foundation.