By the time of Thomas’s birth, the Bonvilles were already one of the pre-eminent families in the south-west of England, even though their elevation to a barony as yet lay in the distant future. Thomas’s father, John, was heir apparent to Sir William Bonville, one of the leading parliamentarians of the last quarter of the fourteenth century, but died in 1396, predeceasing his father by some eight years. Thomas’s elder brother William, aged four, was now heir to the family lands, but in an age of high infant mortality this still left Thomas with reasonable expectations of an eventual inheritance, not least since his grandfather had entailed a large proportion of his estates, including the valuable manors of Shute, Wiscombe and Uppehay, in the male line.
Thomas and Joan Bonville for their part did soon produce a male heir, named John like his paternal grandfather, but soon after Joan died, predeceasing both her father and grandfather. Within the next four years, however, both Sir Hugh Poynings and his father, Lord St. John, also died, leaving Bonville’s young son as coheir to the Poynings estates. Bonville was granted custody of his son’s purparty of the Poynings lands during John’s minority, but this lasted for just another five years until 1434, when he proved his age.
Bonville scarcely needed to defraud his son, for in the spring of 1425 he had married a second time, and his new wife, Lena, the wealthy widow of the Cornish landowner John Wybbury, brought to him her first husband’s extensive estates, all the more extensive since Wybbury had settled on her the greater part of his lands in addition to her legal dower, on condition that she should remain unmarried. In the event that Lena should fail to keep these terms, the lands were to fall to Wybbury’s legitimate issue, represented at the time of her marriage to Bonville by Wybbury’s sole posthumous infant daughter, Joan. Although Lena forfeited her own claim to her first husband’s lands by her marriage to Bonville, the latter lost little time in acquiring the wardship of his stepdaughter and the custody of her lands from the Crown, in return for the sum of 300 marks. Before long, he ensured that the Wybbury inheritance would remain in his family’s possession on a permanent basis by marrying the young heiress to her stepbrother, his own young son, John. In a series of settlements the bulk of John Wybbury’s lands was now handed to panels of feoffees who re-granted them to Bonville and Lena for their lives in survivorship, guaranteeing only their reversion and half the manor of Aveton Giffard to Joan and her descendants.
Bonville’s landholdings placed him in the first rank of the Cornish gentry: he was repeatedly included among those distrained to take up knighthood, in 1434 he was among the men of the county required to take the general oath against maintenance, and in 1450 only Sir John Colshull* and John Arundell of Lanherne were thought to hold more lands in the county than he did. He maintained an impressive household: in October 1439 he ordered from a London embroiderer 22 gowns of his livery, seven of them for gentlemen and 15 for yeomen.
While Bonville was still serving as sheriff, the young earl of Devon formally proved his age, and began the long process of clawing back some of the regional influence that had traditionally pertained to his family. The Hungerford circle, however, proved tenacious, and it was probably as much as a result of his brother’s connexions as of his own standing in Cornwall that Thomas was returned to Parliament alongside the leading lawyer Nicholas Aysshton* in 1439. At the centre, his brother and his friends were still dominant, and just over two weeks into the first session Bonville was appointed to the Cornish bench. It is possible that this appointment remained little more than a mark of status, for there is no evidence that he ever exercised his official powers, and simultaneously his administrative activities also dwindled. Bonville now settled down to the normal life of an country landowner, periodically serving on local juries and acting as an arbiter in his neighbours’ disputes,
By the early 1450s the local rivalry in the south-west between Thomas’s brother, now Lord Bonville, and Thomas Courtenay, earl of Devon, had developed into open warfare, and like many other members of Lord Bonville’s circle, he found himself singled out for attack by local partisans of the earl. On 28 Sept. 1455 his houses at Warleigh and Tamerton Foliot were ransacked and household goods and clothing worth 100 marks carried off.
In recognition of his family’s services to the new Yorkist dynasty Bonville was added to the Devon bench in June 1461, but his Devon property remained too limited to establish him permanently in political society in that county, and he was tacitly dropped again a few months later. The focus of his life in any event remained in Cornwall, where, following Lena Gorges’ death in 1462 he rounded off his possessions by a third marriage to Thomasina, the widow of John Cokeworthy, a Devon gentleman with extensive landholdings in that neighbouring county.
Bonville died on 7 Feb. 1467. He was survived by Thomasina who went on to marry as her third husband Sir Thomas Seymour of Beckington, Somerset. Bonville’s lands were now dispersed among a number of heirs in accordance with their complicated descents and entails. The former Ferrers lands and the reversion of the entailed Bonville estates after the death of Lady Bonville fell to Thomas’s 50-year-old son John. The Wybbury inheritance had some years earlier, in March 1459, been settled on Anne (b.c.1439), John’s daughter from his first marriage to Joan Wybbury, who had married Philip, son and heir of Thomas Bonville’s fellow MP John Copplestone*.