in August 1666: he sent down money by a private hand to be applied to the relief of sick and wounded seamen, and also presented to his old college two pairs of banners wrought with silver thread, and a massive silver trumpet which was long used to summon the college to dinner (the summons has always been made by ‘a clarion,’ as ordained by the college statutes). The motive of the gift to the college appears to have been Williamson's anxiety, though he was a non-resident, to retain and sublet his rooms in college, and he menaced the fellows with ‘inconveniences’ if they did not accede to his wish; the college in reply diplomatically evaded the demand. In small matters, and especially in his management of the ‘Gazette,’ Williamson showed a decidedly grasping and penurious spirit.
With the warm concurrence of his chief, Williamson made various efforts to get into parliament, without meeting at first with success. His candidature failed at Morpeth (October 1666), Preston (May 1667), Dartmouth, and at Appleby, where in December 1667 his hopes were crushed by the intervention of Anne Clifford, the famous countess of Pembroke [for the laconic letter said by Horace Walpole to have been written on the subject by the countess, see Clifford, Anne; that there is some truth in Walpole's story is rendered very probable by State Papers, Dom. Charles II, xxxi. 170]. On 22 Oct. 1669 Williamson eventually succeeded in getting elected for Thetford, and he was re-elected in February 1678–9, August 1679, February 1680–1, and March 1685. He did not sit in the Convention, but he was returned for Rochester in March 1690, while in October 1695, July 1698, and January 1700–1, being elected both for this city and for his old borough, he preferred to sit for the former. He seems to have voted steadily as a courtier, but, except in his official capacity as secretary, rarely opened his mouth in parliament.
In January 1671–2 Williamson became a clerk of the council in ordinary and was knighted. The post of clerk, which had been held by Sir Richard Browne, John Evelyn's father-in-law, had been promised to Evelyn by the king, ‘but,’ explains the diarist, ‘in consideration of the renewal of our lease and other reasons I chose to part with it to Sir Joseph Williamson, who gave us and the rest of his brother clerks a handsome supper at his house, and after supper a concert of music.’ He mentions elsewhere that Williamson himself was an expert performer at jeu des gobelets. On 17 May 1673 Williamson started, in company with Sir Leoline Jenkins [q. v.] and the Earl of Sunderland, as joint British plenipotentiary to the congress at Cologne. There he remained until 15 April 1674 (the letters written to him during his absence were printed for the Camden Society in two volumes, under the editorship of W. D. Christie, in 1874); but although the negotiations, which are detailed in Wynne's ‘Life of Jenkins,’ were tediously prolonged, nothing in reality was effected, and the separate peace between England and Holland (which was suddenly proclaimed in April 1674) was made not at Cologne, but in London.
Before he left England on his embassy it had been arranged between Williamson and his patron Arlington that upon his return Arlington should resign his office as secretary of state, and that Williamson, if possible, should be offered the reversion of the post upon paying a sum of 6,000l. This arrangement was provisionally sanctioned by the king. Meanwhile, in March 1674, Arlington offered to secure the office for Sir William Temple, another of his protégés, and to provide otherwise for Williamson; but Temple refused the offer, remarking to his friends that he considered it no great honour to be preferred before Sir Joseph Williamson.
Williamson returned in June 1674, and was at once appointed secretary of state, being then not quite forty-one; Arlington obtained the more lucrative post of chamberlain. A few days after his appointment Williamson was on 27 June 1674 admitted LL.D. at Oxford, and on 11 Sept. he was sworn of the privy council. Except for the great industry that characterised all Williamson's departmental work, there is little to distinguish his tenure of office as secretary. In September 1674 the new secretary officially announced to Temple as English ambassador at The Hague that the affairs of the United Provinces would henceforth come under his special care. The announcement cannot have been especially agreeable to Temple, and it seems to have been no less distasteful to the Prince of Orange, who saw in Williamson even more than in Arlington an instrument of complete subservience to the French sympathies of Charles II. With respect to another despatch Temple writes, on 24 Feb. 1677: ‘The prince could hardly hear it out with any patience. Sir Joseph Williamson's style was always so disagreeable to him, and he thought the whole cast of this so artificial, that he received it with indignation and scorn.’ He said on another occasion, as on this, that Williamson treated him ‘like a child who was to be fed on whipt cream.’ Temple
