Of distinguished lineage, Thomas was a member of a family which had held the manor of Fawley since the eleventh century. His paternal grandfather and namesake, who sat for Buckinghamshire in no fewer than 14 Parliaments, enjoyed a particularly active career, serving in Edward III’s later campaigns in France, helping to suppress the Peasants’ Revolt, joining the English invasion of Scotland in 1385 and playing a prominent part in local administration. He died aged about 70 in 1406, having outlived Thomas’s father. In October that year Thomas appeared in the Chancery in the capacity of his grandfather’s executor, to swear that the dead man had never received royal letters appointing him to an ad hoc commission in Buckinghamshire.
Thomas was the heir to sizeable estates. Apart from Fawley, these included two manors in Wing, Buckinghamshire, and three others at Upper Clatford, Hampshire, and Helmingham and Marlesford in Suffolk. He also possessed an interest in land at Haddenham in the Isle of Ely.
It is not known if Sackville himself ever campaigned across the Channel, although it is likely that he earned his knighthood by serving the Crown in a military capacity. In any event, such evidence for his career as exists relates to activities at home rather than overseas. Early in his career he acted as a feoffee for William Clerk† of Chipping Wycombe,
By the time of his marriage, Sackville had already begun to play a part in the public affairs of Buckinghamshire, in so far as he had attested the return of its knights of the shire to the Parliaments of 1419 and 1422. He attended at least four other elections in that capacity, including the controversial one of 1429. On 31 Aug. that year he was among those who returned John Hampden II* and Andrew Sperlyng*, a result overturned by the sheriff, Sir Thomas Waweton*, who sent into Chancery a false indenture naming Sir John Cheyne I* and Walter Strickland I* as the men elected. A judicial commission subsequently established that the election of Hampden and Sperlyng should have held good, although by then the Parliament was over. Cheyne was a man with a record of lawlessness and associations with lollardy, and in 1431 he was suspected of involvement in an abortive lollard rising in neighbouring Berkshire. In June that year Sackville was among those commissioned to arrest and bring him before the King and Council, to seize his manors of Drayton Beauchamp and Grove, to confiscate all books, documents and suspicious memoranda they found there and to certify to the Council the details of his armoury and library. The commissioners duly apprehended Cheyne and his brother Thomas, both of whom were briefly imprisoned in the Tower.
Two years later, Sackville himself was returned to Parliament. He was never the most active figure in county administration but his social rank and wealth made him eminently qualified to represent Buckinghamshire as a knight of the shire.
Official duties were not Sackville’s only concern during the mid 1430s, since in this period much of his attention was occupied with important personal affairs. In the summer of 1435 he and his wife conveyed the Sackville manor of Ascot in Wing to his daughter Margery and her husband Thomas Rokes II* and their children, and a year later they took part in the settlement of Riddlesworth and conveyed Marlesford and Upper Clatford to John Hampden II and other feoffees.
Still alive in December 1457, when he was appointed to his last known ad hoc commission, Sackville is likely to have died soon after that date since nothing more is heard of him. He was succeeded by his son or grandson, another Thomas, who died without issue in 1466 and was in turn succeeded by Margery Sackville’s son Thomas Rokes. It may have taken Rokes some years to make good his right to the manor of Fawley, and he did not succeed to another Sackville manor, ‘Crafton’ in Wing, until the late 1480s. Brought to the Kentwood family when another of the MP’s daughters, Maud, married Nicholas Kentwood, it reverted to Rokes after her grandson John Kentwood died without issue in 1487.
