Horace Grocott was born at Napier on 7 April 1880, the fifth child of Joseph Henry Grocott, a sewing machinist, and his wife, Hannah Dryden. The family soon moved to Dunedin, where Horace attended several primary schools before leaving St Leonard's School in 1892. From May 1894 he worked as a messenger with the Post and Telegraph Department while continuing his studies at night, and in November 1899 he was accepted as a cadet at the Dunedin Post Office.
On 5 March 1906 in Dunedin Horace married Ada Gibbs. They were to have three children. Both Horace and Ada had a strong interest in missionary work. After hearing George Allan, the founder of the Bolivian Indian Mission, speak at a meeting, they volunteered for service. With their two-year-old daughter they sailed for Bolivia on 3 July 1909.
For the next five years they worked among the Quechua Indians in the Andes mountains. However, the high altitude and poor living conditions affected their health, and in March 1914 they returned to New Zealand. Although Horace went back to the Post Office, he maintained a lifelong interest in the Mission, serving on its New Zealand council and writing up his experiences in an unpublished manuscript, 'Bolivian episode'.
The Grocotts became closely involved with the Caversham Baptist Church, where Horace led the Young Men's Bible Class Union and supported temperance work and the Christian Endeavour Society. In 1924 he helped some eager lads begin the Baptist Boys' Brigade. It featured military ranks from corporal to general, had a comb band, sang, drilled and marched.
Soon Horace's attention was drawn to the Boys' Life Brigade, a movement founded in England in 1899 and modelled on the Boys' Brigade, started by William Smith in Glasgow. The Caversham Baptist group initially joined the Boys' Life Brigade, and when this amalgamated with the Boys' Brigade in 1926, the Caversham company was officially registered as the lst Dunedin Company of the Boys' Brigade. Grocott was captain until 1931.
The movement spread rapidly. By 1930 Grocott was the honorary dominion secretary and in 1931 he helped form the Boys' Brigade New Zealand Dominion Council. He started the NZ Brigade Boy, a cyclostyled forerunner to the BB News, and supported the appointment of a paid full-time secretary for the movement. In 1928 his wife, Ada, started a company of the Girls' Life Brigade, a British movement affiliated to the Sunday School Union. From this beginning the Girls' Life Brigade spread to many parts of New Zealand, with Ada Grocott as the first dominion president.
In 1931 Horace Grocott was appointed postmaster at Pleasant Point, South Canterbury, serving there until 1941, when he became a supervisor at Temuka Post Office. Wherever he went he introduced the Boys' Brigade. He was captain of the lst Canterbury Company (1931–36), first dominion president of the Boys' Brigade (1932–34), and editor of the BB News (1942–47). In 1939 he was made life vice president.
'HG’, as everyone now called him, organised the first Baptist Church in Temuka, serving as its first secretary, and began a Sunday school for Maori children in Arowhenua pa. He retired from the Post Office in 1945. Eight years later he moved with his family to Miramar, Wellington, where he became a life deacon of the Miramar Baptist Church and wrote its jubilee history.
In 1952 Horace Grocott was made an MBE. When Ada died in Wellington on 13 March 1958, warm tributes were paid concerning her pioneering work and gracious personality. Horace died in Wellington on 10 July 1963, survived by two daughters. A tall, thin man, he was a natural leader with vision, a warm sense of humour and firm Christian convictions. He read widely, kept up a huge correspondence and maintained his enthusiasm for the Boys' Brigade to the end.