William Elliott was sent out to the Cape Colony in 1820 by the London Missionary Society. That same year a William Elliott, presumably him, applied to the government for permission to open a classical and commercial academy, but nothing seems to have come of this. He joined the church of John Philip in Cape Town, but was soon transferred to the Comoro Islands. However, as there was no opening for him there he returned to the Cape in 1822. Returning to England in 1824 he was ordained in Sheffield "to the work of a Christian missionary to the Malays and other heathens in and about the Cape of Good Hope" (The Evangelical Magazine and Missionary Chronicle, February 1825, p. 70). He returned to Cape Town in 1825 under the patronage of the South African Missionary Society, with the encouragement and assistance of the London Missionary Society. He married Georgina J. Caldwell and was stationed at the Caledon Institution (Suurbraak, near Swellendam) in 1830. The next year he moved to Paarl, where most of his plant collection was done. His specimens were sent to W. Harvey*.
In 1839 Elliott was transferred to Uitenhage. From April 1842 he presented a series of four public lectures there, on geology and botany. Leaving Uitenhage at the end of 1845 he visited England in 1846 and the next year became pastor of Barrack Street Chapel, Cape Town. In 1850 he was transferred to George, where he died eight years later. However, in 1856 he was listed in the Cape almanac as living in Kloof Street, Cape Town. A copy of his diary for the years 1844-1851, including a part of his life in Uitenhage and his journey to England, is held in the Cape Town archives repository.
Elliot was a man of outstanding ability. He was at home in Greek, Hebrew, Latin, Dutch and English, and was also a musician. In addition to some sermons he published a series of eight lectures on a comparison between Islam and Christianity (Cape Town, 1828).
Elliott's son, Charles B. Elliot*, became the first General Manager of the Cape Government Railways. His daughter, Isabella Maria, was a plant collector in her own right. She married Rev. Friedrich W. Kolbe, who was also interested in natural history. Their son, Rev. Frederick C. Kolbe* was a prominent naturalist. Elliot's nephew, William C. Faure, was also a plant collector.