As a naval officer, Payne had served with distinction in the West Indies and America until 1783. On his return to England from Italy in 1786 he became the Prince of Wales’s familiar, dubbed ‘Jacko’, and in 1788 the Prince described him as ‘my private secretary’. As such he was the Prince’s indispensable factotum during the Regency crisis, enjoying the confidence of the Prince’s friends and suitors and acting as whipper-in. He was not otherwise active in Parliament, where he was Lord Sandwich’s Member for Huntingdon, giving as his reason that he hated the faces of the majority; but this was after he had been thwarted of office (a seat at the Admiralty board was spoken of for him).
The reason was not far to seek: his increasing involvement in the Prince’s private affairs, which included a continental errand to raise funds in the summer of 1791. In November 1791 he became auditor of the duchy of Cornwall.
Payne, who was friendly with Mrs Fitzherbert and contemptuous of Lady Jersey, the Prince’s latest favourite, fell out with him on his return to England in April 1795. His feelings were exacerbated by the Prince’s treatment of the Princess and of his friend Hugh Seymour Conway. The Prince had recently hoped that Payne would reside next door to Carlton House. In a draft will, 1 Jan. 1796, the Prince referred to the ‘unfortunate misunderstandings’ which had parted them, but enjoined mutual forgiveness. Writing to the Queen, 21 June 1796, he complained of Payne’s ‘infamous conduct’ the year before in taking the part of the Princess (and also of Mrs Fitzherbert) against him. On 10 July Payne submitted his resignation of the auditorship and the keepership of the Prince’s privy seal ( Thomas Tyrwhitt, his replacement as the Prince’s private secretary, was to have them). In doing so he refused any continuation of salary or pension, pointing out that it was as well he had not accepted the Prince’s original offer of the auditorship for life and that the saving might relieve the Prince’s debts. He set aside any implication that he had been clinging to his offices by reference to a previous attempt on his part to resign them.
The Prince had Payne on his conscience and on 8 June 1797 applied to Earl Spencer at the Admiralty for a vacant battalion of marines for him. This was bespoken, but he was placed in command of a detached squadron. He was taken ill after cruising in Biscay in 1798 and resigned with the rank of rear-admiral, February 1799. He had recently been reconciled to the Prince, thanks to his friendship with Mrs Fitzherbert, now once more in favour. At the same time he remained on good terms with the Princess of Wales. On 7 Aug. 1799 the Prince recommended him to Pitt for a naval appointment and he soon afterwards became treasurer of Greenwich Hospital, over the heads of the acknowledged contenders for that office. He sold his house at Brompton and took up residence adjoining Carlton House. He was once more keeper of the Prince’s secrets and anxious to smooth over difficulties between the King and his heir for the benefit of national unity, disclaiming party prejudice. Restored to duchy office on 1 Mar. 1801 he interviewed the new premier Addington on the Prince’s behalf: the Whigs now took a jaundiced view of him, accusing him of intriguing with Mrs Fitzherbert to keep Fox away from the Prince. In 1802 Addington proposed to Lord St. Vincent bringing Payne in on the Admiralty interest for Queenborough. He was unexpectedly defeated. He was still prepared to offer his naval services, but all that remained to him was to be the Prince’s boon companion at the Brighton Pavilion. He died 17 Nov. 1803, with few assets to dispose of. Wraxall described him as ‘one of the most honest and honourable men of his time’.