bart., at Apley, Shropshire, but returned to Oxford on the Restoration, was elected a fellow of his college, and on 16 Feb. 1660–1 took the degree of LL.D. On Dr. Mansell's resignation (1 March 1660–1) he succeeded him as head of the college, and discharged the office with ability. His friend Sir William Whitmore gave him the commissaryship of the deanery of the peculiar of Bridgnorth, Shropshire. The Dean of Westminster (John Earles) appointed him registrar of the consistory court of the abbey. In 1662 he was appointed deputy-professor of civil law in the university, and he was also assessor to the chancellor's court. He had long been a friend of Sheldon, whom he helped in the foundation of his theatre, drawing the conveyance with his own hand; and on Sheldon's translation from the see of London to that of Canterbury, he became his commissary and official for that diocese, and probably his vicar or official-general. He was also accustomed to conduct the foreign correspondence of the university, and was appointed to receive foreign visitors of distinction.
On 11 Nov. 1664 he entered the College of Advocates, and soon afterwards was appointed deputy to Dr. (afterwards Sir) Giles Sweit in the court of arches. On the outbreak of the Dutch war Jenkins was selected by the commissioners of prizes to serve on a committee entrusted with the framing of rules for the decision of prize cases (6 Feb. 1664–5). On 21 March following he was appointed assistant to Dr. John Exton [q. v.], judge of the court of admiralty. On the death of Exton he succeeded to his office, and on the death of Sir William Mericke, judge of the prerogative court of Canterbury, in January 1668–9, he succeeded to his place also. The death of Henrietta Maria at Colombes, near Paris, in the following August, raised an important point of international law. By English law Charles II was entitled to succeed to her personal property as her next of kin, to the exclusion of every one else, the statute of distributions not having then been passed. On the other hand the succession was claimed by Henrietta, duchess of Orleans, on the ground that she was the only one of Charles I's children who was entitled to succeed by French law. The English case was stated by Jenkins, who rested it on the somewhat questionable ground that as a member of the royal household Henrietta Maria could not by her residence in France divest herself of the English domicile which she had acquired on her marriage. Jenkins was also sent to France to assist the English ambassador in recovering the disputed succession. There his arguments or considerations of policy prevailed, and the Duchess of Orleans's claim was set aside. On his return he was knighted, 7 Jan. 1669–70 (Pepys, Diary, 26 March 1667; Cal. State Papers, Dom. 1664–5, p. 427; Strickland, Queens of England, ed. 1845, viii. 264). Jenkins was one of the commissioners in the abortive negotiations for a union with Scotland which took place in the autumn of 1670. From a letter to the Duke of York, written by him during the negotiations, it appears that he was adverse to the project (Mackenzie, Memoirs of the Affairs of Scotland from the Restoration of King Charles II (1821), p. 203). In 1672 Jenkins became one of the managers of the university press. On 11 Feb. 1672–3 he was returned to parliament for Hythe (Letters of Humphrey Prideaux to John Ellis, Camd. Soc., pp. 74–9), and in the following April resigned the headship of Jesus College. Sunderland, who did not act under the commission, Jenkins, and Sir Joseph Williamson [q. v.] were appointed to represent England at the abortive congress which, by the suggestion of Sweden, was summoned at Cologne (5 May 1673) to mediate between Holland on the one part and France and England on the other. Jenkins and Williamson returned in May 1674 to London, where a separate peace had already been concluded between England and Holland (19 Feb. N.S.) On his voyage home, while still in the Meuse off Brielle, Jenkins fired on a Dutch man-of-war for neglecting to lower her flag, upon which the Dutchman obeyed under protest (Mignet, Négociations relatifs à la Succession d'Espagne, iv. 138 et seq.)
The congress of Cologne was followed in 1676 by that of Nymwegen, at which Jenkins again represented his sovereign. Jenkins's colleagues were Lord Berkeley of Stratton [see Berkeley, John first Lord Berkeley of Stratton] and Sir William Temple [q. v.], but the burden of the negotiations fell upon him. He left England on 20 Dec. 1675, and reached the Hague on 3 Jan. (N.S.) Passing Brielle he fell in with two Dutch men-of-war, which saluted him only with their guns, but lowered their pennants on receiving the fire of his yacht. He reached Nymwegen on 16 Jan. (N.S.) Negotiations had hardly begun when Temple was recalled in June 1677, and nothing was done at Nymwegen until after the marriage between the Prince of Orange and the Princess Mary of England (4 Nov.) and the conclusion of an Anglo-Dutch alliance (March 1678, N.S.) In Temple's absence Jenkins showed much discretion in his relations with the French envoys, although he was unable to accept their terms. Louis, however, by his dilatory diplomacy