Glynn was a radical both in politics and religion, a member of the Essex St. group of Unitarians and of the Bill of Rights Society. He was counsel for the printers of the North Briton in 1764, for Wilkes in 1768, and for James Townsend in 1772. ‘A most ingenious, solid, pleasing man’, wrote Chatham on their first meeting in 1770,
In 1768 he stood for Newtown, I.o.W., on the Worsley-Oglander interest, but was defeated. Encouraged by Dunning and Shelburne, with whom he had been connected since the early 60s, he decided to petition.
He made his first speech in the House, on Wilkes’s petition, 23 Jan. 1769. Six other speeches are reported for that session, all connected with Wilkes’s case; and in the conduct of this difficult and intricate business he acquitted himself well. Walpole wrote of the debate of 27 Jan. that he ‘spoke with a clearness, argument, decency, and propriety that was applauded by both sides’; and of his speech on Wilkes’s expulsion, 3 Feb.: ‘Serjeant Glynn gained great fame by the candour of his conduct on the whole proceeding’.
On 6 Dec. 1770 Glynn introduced a motion to inquire into the administration of justice, and he was a member of the committee which drew up the bill of 1772 reducing the number of capital offences. Nearly all his interventions in debate were on constitutional questions or radical motions: and only twice (28 Apr. 1774 and 25 Apr. 1776) is he recorded as having spoken on America. After 1774 his health deteriorated, and his speeches were less frequent. In the debate on Wilkes’s motion concerning the Middlesex election, 22 Feb. 1775, ‘he spoke in great pain, being at that time afflicted with a severe fit of the gout’;
