January 1655-6 (Cal. State Papers, Dom. 1655, p. 90, 1655-6, pp. 1, 23, 100). At the general election in October he was returned to parliament for both Flint and Carnarvonshire, electing to sit for Flint. In February 1655-6 he tried Miles Lindercombe, a plotter against the life of the Protector, who was found guilty and sentenced to a traitor's death, but anticipated justice by poisoning himself in the Tower (Cobbett, State Trials, v. 842). Glynne appears to have shared Hobbes's belief in the necessity of monarchy, while caring little for the hereditary principle. He accordingly supported Alderman Packe's 'petition and advice' that Cromwell should assume the title of king, and was one of the committee appointed on 9 April to receive his 'doubts and scruples' in regard to that matter and endeavour to remove them, to which end, on 21 April, he made a long address to the Protector, which he printed on the Restoration as evidence that he had always been at heart a monarchist. He was continued in office by Richard Cromwell, and presided in the upper bench until Trinity term 1659, when, in view of the approaching revolution, he resigned. He sat for Carnarvonshire in the Convention parliament which met on 25 April 1660, was created serjeant-at-law on 1 June, and on 8 Nov. king's Serjeant, in which character he acted for the crown in the prosecution of Sir Henry Vane for high treason in June 1662 (Hist. MSS. Comm. 5th Rep. App. 63, 153, 154, 168, 196; Wynne, Miscellany, p. 295; Siderfin, Rep. pt.ii. 161-2; Burton, Diary, iii. 175, 182). On 16 Nov. 1660 he was knighted by the title of Sir John Glynne of Henley Park, in Surrey, of which manor he was lord.
He rode in the coronation procession of 23 April 1661, and was thrown from his horse and all but killed by the animal falling upon him. Pepys, regarding him as a rogue and a turncoat, saw the hand of God in this event. Of Glynne's immense ability as an advocate there has never been any question, nor could have been after his speech on the impeachment of Strafford. He was equally distinguished as a judge, his judgments being much admired for their lucidity and method, which, says Siderfin (Rep. pt. ii. 189) brought an intricate case down to the apprehension of every student. His reputation for political honesty suffered severely at the hands of Anthony à Wood, who bore him a special grudge for his part in the suppression of Penruddock's rising. His accuracy, however, may be gauged by the fact that, quoting, as from the 1674 edition of 'Hudibras,' the following couplet:
Did not the learned Glynne and Maynard
To make good subjects traitors strain hard ?
he says that it was written by Butler on the occasion of Penruddock's trial, but not allowed to stand in the 1663 edition, because Glynne and Maynard were then living. In fact, however, Maynard had nothing to do with Penruddock's trial, and was living in 1674. Moreover, the couplet is not to be found in the edition of 1674, or in any subsequent edition, or in the list of various readings appended to Gilfillan's edition. That it was not written by Wood is clear, for it plainly refers to the impeachment of Strafford, which Glynne and Maynard practically managed between them. That Glynne was not particularly scrupulous either as an advocate or as a politician is probable, but neither was he a mere time-server. Only prejudice would doubt his honesty so long as he acted with the presbyterian party. He appears to have been equally opposed to arbitrary government and to anarchy, and to have seen in the monarchical principle, duly limited, the only hope of reconciling stable and strong government with individual liberty. Thus he was equally consistent in urging the crown upon Cromwell and in taking office under Charles II. 'He and Maynard,' says Foss, 'divided the shame of appearing against Sir Harry Vane, their old coadjutor and friend.' In fact, however, Vane, as the head of the independent party, can hardly be described as a coadjutor of Glynne, though he may have been a personal friend; and, in any case, Glynne in appearing on the prosecution was merely discharging his professional duty as king's serjeant, nor does he appear to have taken more than a formal part in the proceedings. Glynne died on 15 Nov. 1666 (Cal. State Papers, Dom. 1666-7, p. 263). He married first, Frances, daughter of Arthur Squib (subsequently through Glynne's influence, Clarenceux herald and teller of the exchequer); secondly, Anne, daughter of John Manning of Cralle, Sussex, and relict of Sir Thomas Lawley, bart., by both of whom he had issue. His eldest son, William, was created a baronet in 1661.
Besides the speeches delivered on the impeachment of Strafford, printed in Rushworth's eighth volume, Glynne published: 1. 'Speech on the presenting of the Sheriffs of London, in Oct. 1644.' 2. 'A Speech to the point of Jus Divinum and the Presbyterian Governments.' 3. 'Monarchy asserted to be the best, most ancient, and legal Form of Government, in a Conference at Whitehall with Oliver, Lord Protector, and a Committee of Parliament, in April, 1658, and made good by several arguments.' London, 1660, 8vo.