Thompson, Robert Lloyd Hall- (1920–92), businessman and politician, was born 9 April 1920 in Belfast, son of Lt-col. Samuel Herbert Hall-Thompson (qv) and Margaret Hall-Thompson (née Maclean). He was educated at Campbell College preparatory school and Campbell College, Belfast, before entering the family business. At the outset of the second world war he joined the Royal Artillery, in which he reached the rank of major, serving (1939–46) on various fronts, most notably in France, and later in the Territorial Army (1946–56). These years of service were later recognised with the award of the Emergency Reserve Decoration and the Territorial Decoration.
His entry into active politics in 1969 saw him following a family tradition with his grandfather, Robert Thompson, having been unionist MP for the Westminster seat of Belfast North (1910–18) and his father unionist MP for the Stormont constituency of Clifton (1929–53) and Northern Ireland minister of education (1944–53). Before 1969 he had been a long-time member of the Clifton Unionist Association but had never sought to hold public office. His decision to stand as unionist candidate for Clifton in the general election of February 1969 was prompted by his support for the reform programme of Capt. Terence O'Neill (qv), the beleaguered prime minister of Northern Ireland. O'Neill had gambled in calling an election to try to strengthen his position in the face of growing unease among sections of unionist public opinion as well as opposition from within his own parliamentary party. This included William Morgan (qv), the sitting MP for Clifton, who just before the election had announced his resignation as minister of health and social services on the grounds of having lost confidence in O'Neill's leadership. The subsequent contest for nomination by the Clifton Unionist Association was a perfect example of the growing fragmentation within Ulster unionism as to the way forward. Initially Morgan was selected, but the manner of his victory was disputed by his opponents and was later challenged in the high court. As a result of this he was forbidden to declare himself as the official Unionist Party candidate or use its resources to contest the election, and in the ensuing confusion Hall-Thompson went forward as an independent O'Neill Unionist candidate, receiving the support of the prime minister in his campaign against Morgan, and won the seat. He did not officially become a member of the Ulster Unionist parliamentary party at Stormont until 1970, but thereafter he gave his wholehearted support to O'Neill and to his successor as prime minister, Maj. James Chichester-Clark (qv).
After the suspension of the Stormont parliament in March 1972, the search for a new form of government for Northern Ireland saw unionist opinion fundamentally split on the way ahead, with some, like Hall-Thompson, following Brian Faulkner (qv) in backing proposals for a power-sharing executive, in association with formal structures to encourage cooperation between the authorities north and south. Hall-Thompson was elected to the new Northern Ireland assembly in June 1973 for the constituency of Belfast North, polling some 5,700 first-preference votes and being elected on the third count. As one of Faulkner's most trusted allies he was appointed chief whip of the short-lived executive, which was brought down by the loyalist workers' strike in May 1974. When Faulkner established his own organisation, the Unionist Party of Northern Ireland (UPNI), Hall-Thompson was one of Faulkner's most loyal supporters. At the elections to the constitutional convention in May 1975, Hall-Thompson was returned once again for Belfast North as one of five UPNI members elected to this new body, charged with devising an agreed form of government (1975–6). However, the convention failed and, after the death of Faulkner in 1977, the UPNI disintegrated, with Hall-Thompson retiring from active politics. He did return, however, to serve as patron of the Friends of the Union in 1986; and in the early 1990s to assist efforts to set up a Conservative Party organisation within Northern Ireland, he became chairman and later vice-president of the Lagan Valley Association.
His pastimes included an interest in horses, even though a war injury meant he could no longer ride. Along with his wife, Alison F. Hall-Thompson (née Leetch; m. 1948), he helped to found the Half-bred Horse Breeders' Society, Ltd, and both were also associated with the Down Royal Corporation of Horse Breeders. In addition Hall-Thompson served as deputy governor of the Maze racecourse until his death. As well as his family's property and motor factory businesses he was active in various charities and voluntary bodies throughout his career – for instance, as a member of the Northern Ireland Hospitals Authority; a vice-chairman and member of the Samaritan Hospital committee (1957–73), Belfast; president and trustee of North Belfast working men's club (1954–90); trustee and honorary secretary of Belfast Newsboys' Club and W. S. Armour Girls' Club; vice-president of Cliftonville Football and Athletic Club; member of the Northern Ireland Nurses' Housing Association; life member and honorary secretary and treasurer of the Not Forgotten Association; and life member of the Royal Ulster Agricultural Society.
He died suddenly at his home near Ballylesson, outside Belfast, on 20 May 1992, some ten weeks after the death of his wife. Hall-Thompson was survived by one son (a Church of Ireland rector) and a daughter.