Thorold’s ancestor, of Yorkshire origin, acquired Marston, five miles from Grantham, in the 14th century, and his grandfather had sat for the borough in 1558. Several of the cadet branches were Papist, but Thorold was an Anglican, and a leading adherent of the monarchy during the Civil War. Under a discriminatory clause of the Newark articles his fine was set at one-third at £4, 160, and he also had to pay £320 to the committee for the advance of money. In 2659 1659 Gervase Holles listed him as prominent among the Lincolnshire Royalists who would be ‘serviceable to his Majesty in his present affairs’. At the Restoration he was proposed as a knight of the Royal Oak with an annual income of £1,500. A few years later his income was said to be ‘near £2,500’.3Lincs. Peds. (Harl. Soc. 1), p. xi; Her. and Gen. ii. 125; Northants. RO, FH113; Lincs. N. and Q. viii. 149; Eg. 2541, f. 362; BL Loan 29/88/83.
Returned from Grantham in 1661, Thorold was a remarkably inactive Member of the Cavalier Parliament. He was twice named to the committee of elections and privileges and added on 26 Oct. 1666 to 1666 to the committee to consider a bill for the regulation of printing. According to Sir Richard Wiseman in 1676, Thorold was ‘very ancient and attends not’. But he was never named as a defaulter at a call of the House, and in 1677 Shaftesbury classed him as ‘doubly worthy’. He died on 4 Mar. 1678.