'Black Billy' Holmes earned his reputation as a master of the black arts of whipping. He was the last Tory Chief Whip in the unreformed House of Commons, but although he continued to play some part in the 1832 election, his inability to secure election to the new House brought to an end his long rule as whip. Characterised by his biographer in the DNB as "adroit and dexterous", his knowledge of the tastes, wishes, idiosyncrasies and family connexions of Tory members was legendary and it made him a most skilful dispenser of patronage and a shrewd party manager. Since Peel, when leader of the Commons, took little interest in party matters, Holmes's position was one of considerable importance to the party.
A good instance of his tactical sense is to be found in the way he forced the Whigs to vote in a debate on Canning's conduct of foreign policy shortly after the latter had succeeded Castlereagh as Foreign Secretary. A motion of censure had been moved by MacDonald and a ministerialist amendment put down. Canning's brilliant defence of his policy left the Opposition resolved not to divide the House, but to let the amendment pass unchallenged. However, Holmes realised what was afoot when no member of the Opposition called out "No", and when the Speaker said "The Ayes have it", he called out "The Noes have it, thus forcing a vote. Most of the Whigs went into the Government lobby and Holmes, voting in accordance with his cry, found that he was amongst a small minority of 21 in the Opposition lobby. He treated the whole episode as an enormous joke, but his action had a serious purpose and his tactic enhanced Canning's credit.
When the result of the 1831 election made the Reform Act possible, Holmes was one of fifteen members of the Conservative party who met at a house in Charles Street, once occupied by Planta, and agreed to use it as their party headquarters and finance it by subscription. Clearly this was to be a point of assembly for the party and it was also to serve as a centre for press management. The independent press fund maintained for this last purpose, which had been under Planta's control was merged into the general Charles Street fund which Holmes controlled. Within six months Holmes had concluded that his Charles Street headquarters was too small and that it was in any case involved too much in press management. In its place stepped the Carlton Club. The Charles Street fund was also of importance in the development of party organisation. Unusually for a whip, Holmes was not made a Lord of the Treasury, although he served as Treasurer of the Ordnance from 1818 to 1830. Though often subject to violent attacks, it is fair to say that his personal honour was rarely questioned and he enjoyed considerable popularity, even amongst his opponents.
William Holmes was the 5th son of Thomas Holmes, a rich brewer of Farmhill in county Sligo, and his wife Anne and came from a family long settled in King's County, Ireland. He was born in Sligo in 1779, and was educated at Trinity College, Dublin, graduating in 1795. He entered the army, served in the West Indies, and was there military secretary to Sir Thomas Hislop He later developed his West Indian connections as agent for Demerara from 1820 to 1833. Upon his marriage with Lady Stronge, widow of the Rev. Sir James Stronge, bart., and daughter of John Tew of Dublin and Margaret Muswell, on 27 October 1807, he left the army and entered parliament for Grampound, Cornwall, in May 1808, and sat for that place till 1812, for Tregony, Cornwall 1812 -1818, for Totnes in Devon 1819 - 1820, for Bishop's Castle, Shropshire, 1820 - 1830, and for Haslemere, Surrey from 1830 until 1832. From 1832 to 1837 he was not in parliament, though in 1835 he unsuccessfully contested Ipswich. In 1837 he contested Berwick-on-Tweed with Sir Rufane Donkin on the reappointment of the Melbourne Ministry and narrowly beat him. There was an unsuccessful attempt to displace him and his colleague in the two-member seat by a petition. Holmes abandoned the seat in 1841 to contest Stafford, but was not elected, and he then quitted parliamentary life, apart from one final attempt to re-enter the House in July 1852 when he contested Dungannon.
Holmes played his part in what many saw as a mania for joint stock companies in the 182os. He was a director of the European Life Insurance and Annuity Office from which he resigned in 1824 and one of the directors promoting the Castello and Espirito Santo Mining Association, founded on a grant from the Emperor of Brazil in 1825. He was also one of those promoting the British Fishing Company in 1825 and a director of the Equitable Loan Company, which came under attack in the letter columns of The Times in 1826.
By special permission from the Duke of Wellington he was allowed in 1829 to give his vote against the ministerial Catholic Relief Bill. Although classed as an 'ultra-tory', he reported on the ultras to the party leadership and it is clear that his ultimate loyalty was to his party and not to any faction within it. He was Treasurer of the Ordnance from 1820 to 1830, and was made a D.C.L. of Oxford on 5 July 1810. He died at his home in Grafton Street, London, on 26 Jan. 1851, leaving one son, Thomas Knox Holmes.