Myddelton’s family had Denbighshire connexions going back to the 13th century and provided the first known Member for the borough seat in 1542. His father acquired a fortune by trade, buying Chirk Castle in 1595 and becoming the greatest landowner in the county. Myddelton was one of the few men of note in North Wales to oppose the King from the outset of the Civil War. But by 1651 he was heavily suspect to the republican regime as a Presbyterian moderate. He appeared in arms for Charles II in the rising of Sir George Booth in 1659, after which Chirk Castle was so far dismantled as to become temporarily inhabitable.4DNB; Keeler, Long Parl. 273; PCC 39 Carr; A. H. Dodd, Studies in Stuart Wales, 125; CSP Dom. 1651, p. 200; 1659-60, p. 162.
Though Myddelton’s health was ‘much impaired by age and the winter’, he resumed his seat on the return of the secluded Members, and was re-elected at the cost of £38 5s.2d. He hired a coach for London on 8 May. Lord Wharton marked him as a friend, but he probably served on no committees and made no speeches. It is unlikely that he attended the second session of the Convention. In 1661 he stood down in favour of his son, who was succeeded on his death by John Wynne, probably with his support. Myddelton drew up his will on 6 Aug. 1666, in which he affirmed his belief in ‘the three creeds established and professed by the Church of England in the time of Queen Elizabeth of blessed memory’. He died on 11 Dec., and was buried in Chirk church at the cost of £754.5Cal. Cl. SP, 496, iv. 604; Chirk Castle Accounts, 85, 86, 141; Cal. Wynn Pprs. 369.