Alan T. Grant-Dalton (sometimes identified as Dalton, A.T. Grant) was the eldest son of civil engineer Alan Grant-Dalton* and his wife Emma Brehm. He was educated at St Andrew's College, Grahamstown, passing the matriculation examination of the University of the Cape of Good Hope in 1896. In 1899 he also passed the university's Survey Certificate examination. He entered the service of the Cape Government Railway in August that year and was admitted as a land surveyor in the Cape Colony in 1901. By 1903 he was stationed at Port Elizabeth, two years later in the office of the resident engineer at Komga, Eastern Cape, and from 1 January 1907 was appointed assistant engineer in the office of the district engineer at Salt River, Cape Town. At that time he lived with his parents in Rondebosch. In 1913 he was stationed in Queenstown.
Grant-Dalton was an associate member of the (British) Institution of Civil Engineers. He became a member of the Cape Society of Civil Engineers during its first year (1903) and remained a member after the society changed its name to the South African Society of Civil Engineers in 1909. In July 1905 J.C. Andrew* and he read a paper, "Notes on the erection of Van Staaden's Bridge, Port Elizabeth-Avontuur Railway", before the society. By 1918 he was assistent superintendent (maintenance) in the South African Railways. In 1931 he was promoted from systems engineer, Cape Town, in the Department of Railways and Harbours to resident engineer (new works) in Cape Town. He retired the next year.