Lennox), by Lady Catharine, eldest daughter of Theophilus Howard, second earl of Suffolk. She was baptised at St. Martin's-in-the-Fields, Middlesex, on 5 Dec. 1640, and married, first, Henry O'Brien, lord Ibrackan, who was buried in Westminster Abbey on 9 Sept. 1678. As heiress to Charles Stuart, duke of Richmond and Lennox [q. v.], his wife brought Williamson a noble fortune. ‘'Twas thought,’ says Evelyn, ‘that they lived not so kindly after marriage as they did before. She was much censured for marrying so meanly, being herself allied to the royal family.’ The alliance offended Danby, who coveted the Richmond estates for one of his own sons, and it may have had something to do with the secretary's fall from office. When the Duke of Richmond died in 1672, Lady O'Brien succeeded to the bulk of his property, but his debts were so heavy that it was found necessary to sell some of the estates to defray them. Under these circumstances the Cobham estates, together with the fine old hall, were bought in by Williamson for 45,000l. In 1679 with his wife's money he purchased for 8,000l. Winchester House in St. James's Square (No. 21), which he tenanted until 1684.
In 1682 he became recorder of Thetford, and on his acquisition of the Cobham estates interested himself not only in Rochester, but also in Gravesend, for which in 1687 he procured a new charter (Cruden's Hist. of Gravesend, 1843, pp. 376 sq.). In May 1690 he was appointed upon the committee to take account of public moneys since William's accession, and in February 1691–2 a false rumour was spread abroad that he was to be lord privy seal. On 21 Nov. 1696, however, Williamson was sworn of the privy council, and on 12 Dec. he was, together with the Earl of Pembroke and Lord Villiers, accredited a plenipotentiary at the congress of Nimeguen. Owing to indisposition he did not arrive in Holland until 8 June. The peace of Ryswick was signed somewhat more than three months later, on 20 Sept. 1697. Williamson stayed on at The Hague in the capacity of ‘veteran diplomatist’ (as he is termed by Macaulay), and on 11 Oct. 1698 the first partition treaty was signed by him at Loo as joint commissioner with Portland. The secrecy with which the treaty had been negotiated excited the wrath of the commons in April 1699, but their full fury fell not upon Williamson but upon Portland and Somers. Williamson returned from Holland in November 1698, and next month it was reported that he would be sent as plenipotentiary to Versailles. He returned, however, to The Hague until the middle of March 1699, when he finally retired from his diplomatic post. He received several visits from the king at Cobham Hall, and in the Rochester Corporation accounts are two heavy bills (May 1697 and 1701) for expenses in connection therewith.
He died at Cobham, Kent, on 3 Oct. 1701, and was buried on 14 Oct. in the Duke of Richmond's vault in King Henry VII's chapel in Westminster Abbey (Chester, Reg. of Burials, pp. 249, 251). Williamson's widow was buried in Westminster Abbey on 11 Nov. 1702, leaving no issue by her second husband.
Rather a man of affairs than a statesman, Williamson appears to have been dry and formal in his manner; he was strictly methodical, scrupulous and exact in the transaction of business, subservient in all things to his chiefs, and severe and exacting towards his subordinates. Music and historical antiquities were his chief relaxations, but his multifarious correspondence can have left him but little time to indulge them. Like most of the statesmen of the day, he turned his industry to good account and managed to accumulate a large fortune during his tenure of office. Some of his early stiffness of manner seems to have worn off, and a gradual rise in Pepys's estimation of him is to be traced through the pages of the ‘Diary.’ Anthony à Wood had no love for the secretary, who on 23 May 1675 ignored Wood's application for the post of keeper of records in the Tower. But he was ‘a great friend,’ Wood admits, to Queen's College and to Queen's College men. Williamson befriended Dr. Lancelot Addison [q. v.], a contemporary with the secretary at Queen's, who dedicated to Sir Joseph, in his capacity of curator of the Sheldonian press, his interesting ‘Present State of the Jews in Barbary.’ The famous essayist was named Joseph after his father's benefactor. Williamson also sent Dr. William Lancaster and Bishop Nicolson (both Queen's men) abroad at the crown's expense, in accordance with a plan of his own for training young men of promise for diplomatic work. Nicolson, when a young taberdar of Queen's, dedicated to the secretary his ‘Iter Hollandicum’ in 1678 (still in manuscript in Queen's Library).
Evelyn's charge of ingratitude is refuted by the dispositions of Williamson's will, in which all institutions and individuals who by blood, affection, or service had any claims upon him were mentioned. To Bridekirk, in addition to a present of silver flagons and chalices for the church, he left 500l. to be distributed among the poor. To the library
