Cunningham, Sir Samuel Knox (1909–76), politician, was born 3 April 1909 in Belfast, youngest among four sons of Samuel Cunningham of Belfast, NI senator and businessman, and his wife Janet Muir Knox, eldest daughter of Dunlop McCosh, solicitor, of Dairy, Ayrshire, Scotland, and Janet McCosh (née Knox) of Riverside, Kilbirnie, Ayrshire. He was educated at RBAI, Fettes College in Edinburgh, and Clare College, Cambridge, graduating in 1931; he was also heavyweight boxing champion at Cambridge University (1931). Called to the bar at the Inner Temple (1939), he served with the Scots Guards during much of the second world war, and was called to the Inn of Court of Northern Ireland (1942), before being invalided from the army in 1943.
On 9 February 1943 he unsuccessfully stood in a Westminster by-election as Unionist candidate for Belfast West, losing to Independent Labour candidate John Beattie (qv) in a four-cornered contest. He became a member of the Ulster Unionist Council in 1943 and remained in this position until his death. In the UK general election of 5 July 1945 he was defeated in the Belfast West constituency for the second time by Beattie. A member of Orpington urban district council in 1954–5, he was first elected to the Westminster parliament for the constituency of Antrim South in the general election of 26 May 1955, easily defeating his Sinn Féin opponent, Michael Traynor. He was a UK delegate to the council of Europe and the WEU (1956–9), parliamentary private secretary to the financial secretary to the treasury (1958–9), and served on the national executive of the conservative party (1959–66). In the general election of 8 October 1959, he easily held his Antrim South seat, defeating Traynor again, and was appointed parliamentary private secretary (1959–63) to the British prime minister Harold Macmillan; he also retained his seat in the general elections of 15 October 1964 and 31 March 1966. During these years he wrote an unpublished work on Macmillan, ‘One man dog’, before deciding not to run for the general election of 18 June 1970.
Cunningham was a significant member of the conservative establishment in mid-twentieth-century Britain, not least through his regular access to Macmillan and membership of the conservative party's national executive. He made an immediate impact in parliament when his maiden speech hit the headlines after he argued in favour of retaining capital punishment, revealing that he was once gravely tempted to commit murder but was deterred by fear of the death penalty. He remained a controversial figure, frequently clashing with the Labour leader and prime minister, Harold Wilson. He opposed any proposals for closer north–south cooperation in the 1960s, befriending the Rev. Ian Paisley (qv), and contributing regularly to Paisley's newspaper, the Protestant Telegraph.
Knox worked for numerous organisations and received several civic distinctions. He became a life member of the English Speaking Union (1943) and of the National Trust (1949), and served as chairman of the national council of YMCAs (1949–67) and a member of that organisation's world alliance (1947–69). In 1956 he was made a freeman of the city of London and became vice-president of the Ulster Rifle Association in 1957, receiving a baronetcy in Macmillan's resignation honours list of 18 October 1963. He was president of the Old Fettesian Association (1967–70), governor of Queen Mary College, University of London (1969–74), grand master of the Masonic Order in Gloucester (1970–76), and deputy grand master of the Orange Order in Ireland (1972). In 1974 he served as vice-president of the boxing club at Cambridge University. He died 29 July 1976 suddenly at his home, Derhams House, Minchinhampton, Stroud, Gloucestershire.
He married (1935) Dorothy Enid Riley, JP, youngest daughter of Edwin Riley, of Bilston, Staffordshire; they had no children.