Clarendon Papers, ii. 302, 374; Nicholas Papers, ii. 72, 113, 123, 344). In the spring of 1655 it was reported that Buckingham had made a secret visit to Dover to confer with one of Cromwell's agents on the question of his return to England and restoration to his estates, and it was also asserted that he was betraying the king's designs to the Protector. But the latter part of the story was certainly untrue (ib. ii. 207, 219, 226, 250, 262, 320). Nevertheless, in the spring of 1656, when Buckingham sought a reconciliation with the king, Hyde urged Charles strongly to show him no countenance (Cal. Clarendon Papers, iii. 113).
In the summer of 1657 Buckingham, tired of exile and hopeless of regaining the king's favour, suddenly returned to England without waiting to obtain the Protector's leave. To marry Fairfax's only daughter, regain thereby part of his estates, and through Fairfax's influence obtain the Protector's pardon, was his design. Mary Fairfax had been promised to the Earl of Chesterfield, and the banns had been twice published at St. Martin's, Westminster; but Buckingham was irresistible, the lady fell deeply in love with him, and the proposed match was broken off. On 15 Sept. 1657 Buckingham and Mary Fairfax were married at Bolton Percy in Yorkshire (Chester, Westminster Registers, p. 255; ‘Autobiography of Brian Fairfax’ in Markham's Life of Robert Fairfax, p. 142). Cowley wrote an epithalamium for their wedding (Poems on Several Occasions, ed. 1700, p. 135). Cromwell and his council regarded this alliance as a presbyterian plot, on the ground that Lady Vere and Major Robert Harley, two of the leaders of that party, had been active in forwarding it. On 9 Oct. the council ordered that Buckingham should be arrested, but he succeeded in evading capture, and remained some time hidden in London. Fairfax vainly appealed to the Protector on behalf of his son-in-law. Cromwell himself inclined to lenity, and finally, about April 1658, Buckingham was allowed to reside at York House in a sort of honourable confinement (Thurloe, vi. 580, 616, 648; Cal. State Papers, Dom. 1657–1658, pp. 124, 169, 196, 357). He found this restraint too irksome, and, going to Cobham to see his sister, was arrested on 18 Aug. 1658 and sent to the Tower (Thurloe, vii. 344).
A passionate scene took place between Fairfax and Cromwell; but Buckingham asserted that if the Protector had lived he would have been certainly put to death (Life of Robert Fairfax, p. 143; Fairfax Correspondence, iv. 253). He did not obtain his liberty till 23 Feb. 1659, when parliament released him on his word of honour not to abet the enemies of the Commonwealth and on Fairfax's security for 20,000l. (Burton, Diary, iii. 370, 435). This did not prevent him from taking the field with Lord Fairfax against Lambert in January 1660; but the soldiers would not allow a known royalist to march with them. Buckingham subsequently claimed that but for his influence Fairfax would not have stirred, and that he therefore had an important share in promoting the Restoration (Fairfax Correspondence, iv. 164–6, 252).
On the return of Charles II, Buckingham became again a gentleman of the king's bedchamber, bore the orb at his coronation (23 April 1661), and was admitted to the privy council (28 April 1662). From 21 Sept. 1661 to 4 March 1667 he was lord-lieutenant of the West Riding of Yorkshire. The estates confiscated by the Commonwealth were restored to him, and, as they brought in 26,000l. a year, he was reputed the richest man in England, and was the most prominent figure in the king's court. In 1663 he was busy in the suppression of the supposed insurrection threatened by the fanatics in Yorkshire (Miscellanea Aulica, 1702, p. 307; Reresby, Memoirs, p. 59). In 1665, during the first Dutch war, he went to sea on board the Prince, attended by Brian Fairfax (Life of Robert Fairfax, p. 137). Clarendon's influence prevented him from obtaining any important office, and in domestic politics all Buckingham's energies were directed to the chancellor's overthrow. In 1663 there was a report that Buckingham and his friends had ‘cast my lord chancellor upon his back, past ever getting up again;’ but the attack was premature (Pepys, 15 May 1663). Buckingham next formed a plan to make Frances Teresa Stuart [q. v.] the king's mistress and govern Charles through her; but here also he failed (ib. 6 Nov. 1663; Grammont, Memoirs, p. 141, ed. 1853). In 1666, however, he succeeded in uniting the opposition leaders in the two houses on the bill for prohibiting the import of Irish cattle, a measure which Clarendon opposed, and Buckingham, partly from hostility to the Duke of Ormonde, supported (Clarendon, Continuation of Life, § 950). But he discredited himself by his want of decency. In a debate on 25 Oct. 1666 he asserted that ‘whoever was against the bill had either an Irish interest or an Irish understanding.’ Lord Ossory challenged him for reflecting upon the whole Irish nation; and Buckingham, after accepting, complained to the House of Lords, which sent Ossory to the Tower (ib. §§ 967–76;
