Armstrong, Harold Reginald (‘Reg’) (1928?–1979), motorcycle champion and businessman, was born, probably in September 1928, in Liverpool, Lancashire, England, the only son of Irish parents, Frederick W. Armstrong and Margery Armstrong (née Wilson). The family returned to Ireland to reside in Rathfarnham Park, Dublin, while he was a child, and he was educated at High School, Dublin. There is some dispute over the date of his birth; the earliest estimates set it in 1926, and different sources give the day as 1 or 3 September. His father was involved in the motor accessory distribution business, and it was through this that Armstrong became interested in machines. During the Emergency (1939–45) he joined (despite being too young) the motorcycle division of the Local Security Force (LSF), where one of the chief instructors was Stanley Woods (qv), one of Ireland's greatest-ever motorcycle champions.
After the war Armstrong began racing competitively, and in 1947 he rode in the Manx Grand Prix for the first time, finishing fifth in the Junior race on an Excelsior Manxman. In 1948 he came fourth in the Senior race. He competed in the Isle of Man TT during 1949–55, winning the Senior TT in 1952 on a Norton, and finished second in the Junior race. In all he had five top-three finishes. His 1952 win was one of the most extraordinary victories in TT history, when he freewheeled the last 200 metres after suffering a broken chain. He also had a total of seven World Championship Grand Prix wins: the German 350 and 500 cc GP, and the Isle of Man Senior TT in 1952; the Ulster and the Swiss 250 cc races in 1953; the Spanish 500 cc in 1955 and the German 500 cc in 1956. He finished runner-up in the World Championship on five occasions: twice in the 500 cc (1953, 1955); twice in the 350 cc (1949, 1952) and once in the 250 cc (1953). He was particularly unfortunate in 1952, when the 350 cc title was within his grasp until he snapped a chain in the last race of the season. Domestically, he also won the International North-West 200 in Portstewart, Co. Londonderry, in 1954 and the Leinster 200 five years in a row (1951–5). He initially rode for AJS and Velocette, but rode for the Norton team in 1952, and the following year he moved to Gilera in Senior events and German manufacturer NSU in Junior races. Armstrong retired from competitive cycle racing in 1956 and briefly took up car racing, coming fourth in the International Junior Scratch race in the Phoenix Park in 1961, although he never took part seriously. In 1963/4 he was manager of Honda's Grand Prix racing team, a team that included the legendary Mike Hailwood.
He was also a successful businessman, establishing his own company, Reg Armstrong Motors Ltd, initially starting in the motor trade by obtaining the distribution and assembly rights for NSU, one of his former teams. The mainstay of his business, however, was the Honda motorcycle and the Opel motorcar agencies for Ireland, and he established an assembly plant at Ringsend in Dublin, where up to 200 people were employed in the 1970s before European legislation put an end to vehicle assembly in Ireland. An excellent shot, he was chosen as captain of the Irish clay-pigeon shooting team that participated at the 1978 world championship in Korea. He was also a keen field sportsman, being adept at both shooting and fishing, and also had a keen interest in farming, being widely acknowledged as a European expert in Charolais cattle. Latterly a resident of Ashford, Co. Wicklow, he died 24 November 1979 in a car accident near Avoca, Co. Wicklow, and is buried in Enniskerry.
He married first (1954) Rosemary Adams from Ballymena, Co. Antrim, and secondly, in England, Eileen (maiden name unknown); there were two daughters from his first marriage.