Brockhill was the third member of his family to sit for Kent in Parliament; his namesake Sir Thomas had done so five times between 1337 and 1353, and the latter’s son, Sir John, was returned in 1378. His precise relationship to these two men is not known, but the fact that he never occupied the family’s principal residence at Saltwood suggests that he was Sir Thomas’s younger son or nephew.
From early on in his career Brockhill was often placed in positions of trust. By 1371 he had become a close friend of Sir Walter Paveley (son of the Garter knight of the same name), for whom he acted not only as a feoffee of the manor of Boughton Aluph and of Paveley’s other estates but also, as named in Sir Walter’s will in 1379, as ‘distributor et ministrour’ of the testator’s goods. Paveley thought so highly of him as to supplement a gift to him of £13 6s.8d. with a legacy for life of an annuity of the same amount charged on the estate at Boughton. Before too long Brockhill was also named as executor of the will of Nicholas, son of Sir John Kyriel, another noted landowner in the county.
At the end of 1380 Brockhill went overseas as captain of Marck castle, in which capacity he served until the spring of 1382. His first election to Parliament for Kent followed later that year, but it was his kinsman, Sir John Brockhill, who was appointed as sheriff of the county in November, the month after the Parliament was dissolved. Sir John died in office in May 1383, having named Thomas as one of his executors, and within a few days the latter took over the sheriff’s duties. He remained in the post for 18 months. In June 1387 he obtained royal letters of protection as going on the King’s service to Calais in the company of Roger Walden, the treasurer there, but these were cancelled in the following spring since he had failed to depart. In 1391 he and his wife conveyed their property in Murston, Elmley and elsewhere to John, Lord Devereux, then steward of the King’s household and warden of the Cinque Ports, but, this transaction apart, there is no evidence that Brockhill was ever closely acquainted with figures of political importance.
During the 1380s and 1390s Brockhill’s employment in the capacity of a feoffee of landed estates continued with him acting on behalf of Helming Leget and a Kentish lawyer, William Makenade.
