Born at his grandfather’s Suffolk property of Rishangles, near Thorndon,30 The erroneous claim that he was born at Bradfield probably originates with E. Foss, Judges of Eng. vii. 100. Grimston followed his elder brother Edward to Emmanuel College, Cambridge at the age of 16. From there he entered Lincoln’s Inn to pursue a legal training, and in 1626 became involved in an affray with Arthur Pyne*,31 LI Black Bks. ii. 263. perhaps over the hand of the Essex heiress Grace Barlee, whom Pyne later married. It may have been shortly thereafter that Grimston abandoned his studies, for on the death of Edward in 1624 he had become the heir to his father’s Essex and Suffolk estates. However, he returned to his books after Sir George Croke, one of the justices of Common Pleas, threatened to forbid him from marrying his daughter Mary, with whom Grimston had fallen in love.32 Bp. Burnet’s Hist. of His Own Time (2nd edn.), ii. 68. He also joined an informal circle of young lawyers which met during vacations at Mistress Percy’s house in Fleet Street to exercise ‘their wits and learning in the imitation of Star Chamber proceedings’.33 Ibid. 58. This now-found love of the law meant that in April 1629 Grimston was permitted to marry Mary Croke at St. Dunstan-in-the-West, Fleet Street. After the ceremony the couple were ‘accompanied by many friends’ to Bradfield Hall, where Grimston’s father provided a sumptuous feast ‘and high entertainment’.34 Diary of Bulstrode Whitelocke ed. R. Spalding (Recs. of Social and Ec. Hist. n.s. xiii), 56.
Following the death of his brother-in-law Christopher Herrys in October 1628, Grimston was returned to Parliament for Harwich, presumably on his father’s interest, but played no recorded part in the 1629 session. Called to the bar in November 1628, he subsequently acquired the recorderships of both Harwich and Colchester. A parliamentarian of Presbyterian sympathies during the civil wars of the 1640s, Grimston represented Colchester during the Short and Long Parliaments, but was secluded at Pride’s Purge after urging the Commons to ratify the Treaty of Newport and Bradfield Hall was plundered. Forced into early retirement, he purchased a new seat at Gorhambury, in Hertfordshire and edited the law reports of his father-in-law, which were published in 1655. Elected to the second Protectorate Parliament for Essex in 1656, he was again barred from taking his seat, but was readmitted to the Long Parliament in February 1660. Later that year he was appointed to the council of state, by which time he may already have opened secret communications with the royalist Court in exile. As Speaker of the Convention he greeted Charles II on the latter’s arrival at Whitehall in May 1660. His part in the Restoration was rewarded with the mastership of the Rolls.35 Clarendon, Hist. of the Rebellion ed. W.D. Macray, vi. 214; N. King, Grimstons of Gorhambury, 11-13. He died from a fit of apoplexy in January 1685 and was buried at St. Michael’s church, St. Albans, having first made a place for himself in the vaults by disinterring the remains of the former lord chancellor (Sir Francis) Bacon*.36 J. Aubrey, Brief Lives ed. A. Clark, i. 66; HMC 1st Rep. 56. Four portraits of him hang at Gorhambury, one by John Riley, one by Mary Beale and two by unknown artists.37 King, 14-15.