MOSTYN, Thomas (1651-92), of Gloddaeth, Caern.

Published in The History of Parliament: the House of Commons 1660-1690, ed. B.D. Henning, 1983
Available from Boydell and Brewer



Family and Education

bap. 27 May 1651, 3rd but 1st surv. s. of Sir Roger Mostyn, 1st Bt. of Mostyn, Flints., being 1st s. by 2nd w. Mary, da. of Thomas, 1st Visct. Bulkeley of Cashel [I]. educ. Christ Church, Oxf. 1667. m. by 1672, Bridget, da. and h. of Darcy Savage of Leighton, Cheshire, 7s. (4 d.v.p.) 3da. suc. fa. as 2nd Bt. 4 Oct. 1690.1

Offices Held

J.p. Flints. 1672-80, Caern. 1673-80, ?1689-d.; commr. for assessment, Caern. 1673-80, Flints. 1673-4, Anglesey, Flints. and Merion. 1679-80, Anglesey, Caern. and Flints. 1689-91, Merion. 1689-90; dep. lt. Caern. and Flints. 1674-80, Caern. 1689-d.; capt. of militia horse, Caern. by 1675-7; col. of militia ft. Caern. and Merion. by 1675-7; sheriff, Anglesey 1691-2.2


Mostyn came from an ancient Welsh family which had been prominent before the English conquest, but took their name from an estate in Flintshire acquired by marriage in the 15th century. They first sat for the county in 1545. His father, an ardent Royalist, was governor of Flint Castle at its surrender on 24 Aug. 1646. He compounded for £852, though family tradition estimated his total losses at £60,000, and he had to abandon the family seat during the Interregnum. Their fortunes were restored by Mostyn’s marriage with a Cheshire heiress and the exploitation of the deposits of coal and lead on their estates. After his marriage Mostyn settled on the family property in Caernarvonshire, three miles from Conway, and became an active militia officer. But when he complained about the influence of the Roman Catholic Lady Powys on the militia, the Marquess of Worcester (Henry Somerset), incensed at this attack on his sister, withdrew his commission.3

Mostyn represented Caernarvon Boroughs in the Exclusion Parliaments. With a Tory father and a Roman Catholic wife, he was left unmarked on Shaftesbury’s list, and was appointed to no committees in 1679. Although he was fluent in Welsh, his English was apt to be clumsy, and he occasioned loud laughter in the debate on security against Popery on 27 Apr. by describing the Papists as receiving encouragement from the Duke of York’s quality, not his understanding, by which he apparently meant not to impugn the Duke’s intellect, but to absolve him of knowledge of the Popish Plot. Undeterred, he continued his speech by remarking that he considered the Duchess of Portsmouth quite as dangerous as the heir to the throne. He voted for exclusion and was removed from the lieutenancy and the commission of the peace. He protested vigorously to Lord Worcester at his dismissal, referring to the proofs of loyalty given by his family and yielding to nobody in the expression of his devotion to the King and the established Church.4

In the second Exclusion Parliament, Mostyn was appointed to the committees to receive information about the Plot, to examine the conduct of Sir Robert Peyton and to consider the bills for the abolition of the court of the marches and for establishing Protestant unity. On 7 Jan. 1681 he moved for an Association, and gave the House an account of his dispute with Worcester. He left no trace on the records of the Oxford Parliament, and probably did not stand again, but devoted himself to Welsh studies. During the Revolution he took action against the local Papists. He was excused from serving as sheriff of Caernarvonshire in 1689, but was pricked for Anglesey in 1691. He died in the following year, when he was replaced on the assessment commission by his son, the 3rd baronet, who sat in Parliament as a moderate Tory from 1701 till his death.5

Ref Volumes: 1660-1690

Authors: A. M. Mimardière / John. P. Ferris


  • 1. L. N. V. Mostyn and T. A. Glenn, Fam. of Mostyn, 150-6.
  • 2. Cal. North Wales Letters (Univ. Wales Bd. of Celtic Studies, Hist. and Law ser. xxiii) 168, 171, 177.
  • 3. Mostyn and Glenn, 45, 135, 144-5; Cal. Comm. Comp. 1666; T. Dingley, Beaufort’s Progress, 95; Nat. Lib. Wales Jnl. vi. 253.
  • 4. CSP Dom. July-Sept. 1683, p. 323; Grey, vii. 139; Cal. North Wales Letters, 177.
  • 5. HMC 12th Rep. IX, 110, 114; A. H. Dodd, Studies in Stuart Wales, 227; Cal. North Wales Letters, 179; CSP Dom. 1689-90, p. 50.