Moore, Sir William (1864–1944), 1st baronet, barrister, and politician, was born 22 November 1864 in Antrim, eldest son of William Moore (1826–1901) of Moore Lodge, Co. Antrim, physician and former high sheriff of Antrim, and his wife Sidney Blanche (d. 1919), daughter of Capt. Abraham Fuller of Woodfield. William was educated at Marlborough and TCD, where he was an outstanding student, president of the Philosophy Society, and gold medallist for oratory. He graduated in 1886 with a BA in classics and history. He entered Lincoln's Inn and was called to the Irish bar in 1887, thereafter practising on the north-east circuit. In 1899 he took silk, and was the same year elected unionist MP for Antrim North. He held this seat until 1906, when he lost it by a narrow margin and was immediately invited to stand for Armagh North, which he held from 1906 to 1917. He was senior crown prosecutor for the city of Belfast (1915–17), and in 1917 he was made a high court judge. He successfully combined the careers of law and politics; though for the crucial first two decades of the century, politics commanded his attention.
Moore was an Orangeman and an Ulsterman and he put all the resources of his powerful physique and strong invective towards maintaining the union for his part of the country. He was in that tradition of Ulster loyalism which combined nominal loyalty to the tory government with flagrant defiance. The Balfour government and even fellow Ulster unionists found his extremism alarming, though he earned their admiration for his effective routing of the independent and populist unionist T. W. Russell (qv) between 1903 and 1906, Moore's full-blooded speeches being given full credit for purging Ulster of Russellism.
The devolution crisis of 1904 was the occasion for Moore's greatest initiative. Disgusted with the Dublin administration – most especially Antony MacDonnell (qv), Wyndham's catholic Irish under-secretary – Moore (together with Charles, brother of James Craig (qv)), established the Ulster Unionist Council in March 1905. The council, which fused local unionist associations, the Orange lodges and unionist dignitaries in one policy-making body, played a crucial role in defeating the third home rule bill and has never diminished in importance since its inception.
As early as January 1911 Moore was cogently defending Ulster's right to armed resistance, and he favoured with uncompromising force the amendment to the third home rule bill (1912), which excluded the four counties of Antrim, Armagh, Down, and Londonderry. He later observed that the formation of the Ulster Volunteer Force in January 1913 was largely responsible for the British government's willingness to accept partition. He lived to see all his hopes crowned, and had little regret for the loss of the rest of the country to nationalism. After the government of Ireland act (1920), he expressed satisfaction at being cut off from southern protestants, whom he denounced vehemently as cowards.
With his political ambitions satisfied he devoted the rest of his life to the legal system in Northern Ireland. In 1921 he transferred to the NI supreme court, where he served four years before being made lord chief justice of NI, from which position he oversaw the establishment and staffing of the courts. He was created a baronet in 1932. He retired in 1937, and died 28 November 1944 at his seat, Moore Lodge, Kilrea, Co. Antrim. He married (1888) Helen Gertrude (d. 1944), daughter of Joseph Wilson of Dublin; they had two sons and a daughter.