heiress of Major Robert Gore of Shereton, Wiltshire, was born at Battin Warwick, on the river Bandon, near Kinsale, on 31 Dec. 1635.
His father, Robert Southwell (1607–1677), was the son of Anthony Southwell, esq., who, with his elder brother, Sir Thomas Southwell (d. 1626), came first to Ireland in the reign of James I as an undertaker in the plantation of Munster, and having married Margaret, daughter of Sir Ralph Shelton of Norfolk, died at Kinsale in 1623. Robert, who succeeded him, was appointed collector of the port of Kinsale on 22 July 1631. He resided there during the whole period of the rebellion, and, with the rest of the inhabitants, took his share in the defence of the town against the Irish (Mallow Proceedings, A/61, 39, ff. 4–5). In 1648 he was instrumental in provisioning the fleet under Prince Rupert, being then blockaded by Blake and Deane, and was consequently condemned under the Commonwealth, by the ordinance of 2 Sept. 1654, to forfeit one-fifth of his property (Prendergast, Cromwellian Settlement, p. 172). He was removed from his post of collector of Kinsale, but subsequently found so much favour with the government of the Commonwealth as to be employed on several commissions, and on 5 Oct. 1657 he was elected sovereign of Kinsale (Caulfield, Council-book of Kinsale, p. 29). After the Restoration he obtained a grant of the forfeited estate of Philip Barry Oge in the liberty of Kinsale, including Ringcurran, which was confirmed to him by letters patent of 16 June 1666. He was recognised as one of the most active and influential personages in Kinsale, and rendered valuable assistance to the Earl of Orrery in strengthening the fortifications of that town in anticipation of the attacks of the Dutch, and was rewarded by the governorship of the newly erected fort at Ringcurran (Orrery, State Letters, ii. 266, 318). He was on 20 Sept. 1670 appointed vice-admiral of Munster, and apparently about the same time he was admitted a member of the provincial council. He died on 3 April 1677, and in accordance with his will, dated 4 Nov. 1676, was buried in his own tomb in the eastern aisle of Kinsale church, where, under a neat monument of Italian marble with a long inscription, are also interred his wife, who died on 1 July 1679, aged 66, and his infant son Thomas. He had, besides, two daughters, Catherine—born on 1 Sept. 1637, married on 14 Feb. 1655 to Sir John Perceval, died 17 Aug. 1679, likewise buried at Kinsale—and Anne, married to Ralph Barney of Wyckingham, Norfolk.
Robert seems early to have been destined for a diplomatic career, and, going to England in 1650, he passed through Queen's College, Oxford (matriculating 24 June 1653 and graduating B.A. 28 June 1655), and Lincoln's Inn, which he entered in 1654, completing his education by continental travel in 1659–1661. Of his sojourn in Italy and the acquaintances he made in Rome he has left a meagre account in a sort of commonplace book that he kept at the time (Egerton MS. 1632). Returning to England in 1661, he shortly afterwards became acquainted with Sir William Petty [q. v.] The acquaintance ripened into a lifelong friendship, which was further cemented by Petty's marriage, in 1667, with Southwell's cousin, Lady Fenton. He appears as clerk to the commission of prizes in 1664, and in September of that year was appointed one of the clerks to the privy council. He was knighted on 21 Dec. 1665, and the same year appointed deputy vice-admiral of the provinces of Munster, succeeding to the vice-admiralty itself on the death of his father twelve years later. Meanwhile in November 1665 he was appointed envoy to the court of Portugal, with the object of effecting a peace between that country and Spain, payment being made to him under a privy seal warrant of 1,000l. for secret services (Cal. Dom. 1665, p. 46). He reached Lisbon early in the following year, took part in the coup d'état that ended in the deposition of Alphonso VI, and had the satisfaction of bringing his mission to a satisfactory conclusion by the peace of Lisbon on 13 Feb. 1668, but not without exciting the jealousy of the Earl of Sandwich, who held the post of ambassador extraordinary to the court of Spain, and desired to have the entire credit of the treaty (cf. Pepys, Diary, vii. 312; Southwell's correspondence in connection with the treaty was published in 1740). After the conclusion of the treaty he returned to England, but was in April that year again appointed envoy extraordinary to Portugal, for the double purpose of attending to the embarkation of the English auxiliary forces returning to England and concluding a treaty of commerce with Portugal. He sailed from Deal on 16 June; but his business detaining him in Lisbon for fully a year, and no provision having been made for his prolonged stay, he became considerably involved in debts, which had not been paid off four years later (Cal. Dom. 1670 pp. 130, 192, 1671 p. 499). Returning to London in August 1669, he took up his residence in Spring Gardens. In the following autumn he spent a short holiday with his father at Kinsale, and in May 1671, having been appointed a chief commissioner of excise, with a salary of 500l.
