One of the richest and most powerful landowners in Derbyshire, Gresley was heir to both the estates of his paternal grandfather, Sir John† (who outlived Sir Thomas’s father by at least six years) and the widespread possessions of his mother, Thomasina Wastneys. During the later 14th century, the Gresleys successfully extended their territorial influence, which was initially confined to the area around Drakelow, Linton, Lullington and Gresley in Derbyshire, by twice marrying into the Wastneys family. They thus acquired the manors of Colton in Staffordshire, Braceborough and Carlby in Lincolnshire, Osgathorpe in Leicestershire and Seaton in Yorkshire, as well as other property, rents and advowsons in these four counties. Not long before his death, in about 1395, Sir John Gresley settled all his own estates upon his grandson, who took on the lease of his mother’s manor of Braceborough at a rent of £26 a year soon afterwards. Thomasina was dead by July 1405, for on that date Sir Thomas conveyed the land she had left him to an august body of feoffees, including Thomas Langley, bishop of Durham and chancellor of England, and Philip Repingdon, bishop of Lincoln. Although she was not an heiress in her own right, Sir Thomas’s wife, Margaret, also contributed notably to his annual income. During the Hilary term of 1397 her father, Sir Thomas Walsh, made an arrangement whereby the couple were to pay him £29 a year for life as tenants of land in the Warwickshire village of Monks Kirby and various parts of Leicestershire, which was to become their own property when he died. Since he lived for only a few more months, the settlement worked entirely to Gresley’s advantage. The latter made no substantial additions to his estates after his mother’s death, and from then onwards he may reasonably be assumed to have been worth the £200 a year in landed revenues on which he was taxed in 1436. His property in Derbyshire alone was said to produce £65 p.a. in 1412, so this figure probably represents something of an understatement. He also possessed the right of presentation to the Augustinian priory at Gresley, one of his ancestors’ foundations, and to the parish church of Dalbury in Derbyshire.
Apart from his marriage, very little is known about Gresley’s early life, which appears to have passed without incident. A Thomas Gresley of Edingale was pardoned in February 1398, but since there is no other evidence to connect the MP with this part of Staffordshire, the reference possibly concerns another man. Not long afterwards, however, Gresley became involved in an acrimonious and protracted quarrel with his neighbour, the abbot of Burton on Trent. The abbot subsequently alleged that towards the end of Richard II’s reign Sir Thomas not only began to enclose common land belonging to the abbey and demand services from its tenants, but also repeatedly assaulted the monks themselves and caused considerable damage to their property. A commission of oyer and terminer was set up in December 1405 to investigate these complaints, and in the following March the two parties surrendered mutual sureties of 1,000 marks as a guarantee of their future good behaviour towards each other. The recognizance of November 1409 by which Gresley bound himself in £100 to Archbishop Arundel of Canterbury may likewise have had something to do with the affair, and although the conditions attached to it do not survive they possibly concerned an informal attempt at arbitration. Sir Thomas proved too powerful an adversary, even so, and in about 1414 (or perhaps even later) the abbot had again to seek the protection of the law after a further series of attacks upon his person.
Gresley’s standing in the north Midlands is underlined by his return to at least six Parliaments as a knight of the shire for either Staffordshire or Derbyshire, the regularity of his appointment to royal commissions, and, from about 1405 onwards, his popularity as a feoffee-to-uses. A large number of local farmers and landowners called upon his services in this respect, often together with those of his eldest son, Sir John. Among the more distinguished persons who made him their trustee were Sir Roger Fiennes (whom he also assisted in the purchase of a wardship in 1441), his wife’s kinsman, Sir Thomas Boyville (on whose behalf he fought an action in Chancery), John Swynnerton and Nicholas and Roger Bradshaw.
The network of marriage alliances which Sir Thomas arranged for his children further helped to establish the Gresleys among the leading members of county society. In about 1409, his elder son married Elizabeth, the daughter of Sir Thomas Clarell of Tickhill and Aldwark in Yorkshire, for whom he later acted as a mainpernor. His daughters, Joan and Margaret, did equally well for themselves, becoming the wives, respectively, of Sir Thomas Blount (d.1456), treasurer of Normandy, and Thomas Astley of Patshull, who was related to the Beauchamp earls of Warwick. Sir John Gresley and his brother-in-law, Blount, both prospered under the patronage of John, duke of Bedford, and Gresley had the satisfaction of seeing his son become lieutenant-general of Rouen. A third daughter is said to have married into the Curson family of Croxall in Derbyshire.
Sir Thomas’s importance to the Crown was also growing throughout this period: in 1400 he received an annuity of £26 payable for life from the duchy of Lancaster honour of Tutbury, an award which was confirmed to him by Henry IV’s successors. Together with his elder son he fought on the first French expedition of 1415, providing a retinue of three men-at-arms and nine archers. He was at this time acting with Sir Robert Francis as one of the joint custodians of Repton priory, with particular responsibility for the reform of certain financial abuses there. Shortly after, he and the lawyer, Peter de la Pole, another loyal retainer of the duchy of Lancaster, secured for themselves the custody and marriage of the two daughters and coheirs of Robert Dethick for the comparatively modest sum of £40, although both were expected to work hard to justify such preferential treatment.
Except for serving on a few royal commissions, Sir Thomas took no real part in public life after 1427, and not much evidence survives about him from then until his death 17 years later. How far his decision to retire was affected by the events surrounding the Nottinghamshire parliamentary elections of 25 Aug. 1427 we shall never know, but there can be no doubt that, as sheriff and returning officer, he not only acted without first receiving the necessary writ of summons, but also completely disregarded the law with regard to electoral procedure in the interest of his own nominees, Hugh Willoughby and Ralph Mackerell. As a result of a government inquiry held in the following February, Gresley was ordered to pay the statutory fine of £100; and he never served as sheriff again. Curiously, in view of his apparent friendship with Mackerell, he also stood accused of using his official position to help Sir Thomas Rempston I’s redoubtable widow, Margaret, extort damages of £2,000 from him, at least if an appeal addressed by Mackerell to the Crown for help at this time is to be believed. Not surprisingly, then, we find Sir Thomas among the leading residents of Derbyshire who were required, in May 1434, to take the generally administered oath not to support persons breaking the peace. Five years later his alleged exploitation of the estates of his brother-in-law, Thomas Walsh, which had been committed to him in 1422 because of the latter’s recurrent insanity, became the subject of an investigation by a specially appointed commission of oyer and terminer. Its findings revealed that Gresley and his wife were indeed responsible for ‘wastes and destructions’, and the property was entrusted to others.