The fifth son of James KingDean of Raphoe and his wife Anne Walker, he was educated at Eton and matriculated at Christ Church, Oxford in 1777, graduating B.A. in 1781, M.A. in 1784. King became a Home Office law clerk in January 1791. He had the support of William Grenville, 1st Baron Grenville, at that time Home Secretary, and at the end of the year became Permanent Under-Secretary of State for the Home Department. Under Grenville's successor Henry Dundas, King was belonged to the circle gathering government intelligence across departments, including also Richard Ford, Francis Freeling, William Huskisson, Evan Nepean, and William Windham. One surveillance operation in which he was involved was on Alfoxton House in August 1797, where William Wordsworth was staying, and about which James Walsh reported to King because of the presence of John Thelwall, an operation partly prompted by Dr. Daniel Lysons. Windham, a politician rather than an official, used King as an intermediary with Greville in 1792, when entering a covert role. In 1794 Nepean moved on from the Home Office, leaving King the senior of the Under-Secretaries of State, and he started to plan for a future seat in Parliament. After the passing of the Aliens Act 1793, King also worked in the Alien Office. From an initial task of dealing with correspondence, assigned at the end of 1794, he took on further duties as the Alien Office addressed intelligence needs and countered subversion. In 1798 he became a joint superintendent of aliens, with Flint and Wickham. He stayed at the Home Office until 1806, when Grenville became Prime Minister. In 1806 King was Secretary to the Treasury, with Nicholas Vansittart. This position required that he have a seat in the House of Commons, to act effectively as patronage secretary for Grenville. Enniskillen was the constituency found for him. King, however, was uncomfortable in Parliament; and asked to be moved. He was replaced at the Treasury, and as MP, by William Henry Fremantle, in September of that year. Eased out of Parliament, King became comptroller of army accounts, a post he held for the rest of his life.
William Moss, rector of Long Crichel, Dorset, graduated from Christ Church, Oxford in 1817. He married Elizabeth Margaret, daughter of Very Reverend Latham Coddington, Dean of Kilfenora.
Marianne married in 1814 Walter Campbell, of Sandilands, Lanarkshire
Harriet married in 1825 William Henry Blaauw. Together with William, she had one daughter
Caroline Margaret married in 1819, General Sir William Cornwallis Eustace of Sandford Hall, Braintree, and died before 1830, leaving issue.
Anne Elizabeth married in 1821, her cousin, Thomas Venables, Private Secretary to Lord Sidmouth & Sir Robert Peel
Katherine Judith married on 24 Oct 1822, Henry John Adeane of Babraham, Cambridgeshire.
Robert of Chester Street, London, married his cousin, Georgiana Anne Carleton
Emily married in 1826 William Henry Harford, of Barley Wood, near Bristol
Elizabeth was engaged to Brook Henry Bridges, elder son of Reverend Brook Henry Bridges, rector of Danbury, Essex
