William Smith, the son of Samuel Smith, a grocer, was born in Clapham on 22nd September 1756. He was educated at the Daventry Academy where he began to come under the influence of Unitarians. He went into the family business and by 1777 had become a partner.
On 12th September 1781 he married Frances Coape. The couple moved to Eagle House on Clapham Common. They had five daughters Frances, Joanna Maria, Julia, Anne and Patty. Frances Smith later married William Nightingale and was the mother of Florence Nightingale.
Smith held radical political opinions and was a member of the Society for Constitutional Information in 1782, an organisation established by Major John Cartwright. Other members included other radicals such as Granville Sharp, Josiah Wedgwood, John Horne Tooke, John Thelwall and Joseph Gales. It was an organisation of social reformers, many of whom were drawn from the rational dissenting community, dedicated to publishing political tracts aimed at educating fellow citizens on their lost ancient liberties. It promoted the work of Tom Paine and other campaigners for parliamentary reform.
In 1784 Smith became the Member of Parliament for Sudbury in Suffolk. In the House of Commons he supported the reform program of the Whigs. In June 1786 Thomas Clarkson published Essay on the Slavery and Commerce of the Human Species, Particularly the African. As Ellen Gibson Wilson has pointed out: "A substantial book (256 pages), it traced the history of slavery to its decline in Europe and arrival in Africa, made a powerful indictment of the slave system as it operated in the West Indian colonies and attacked the slave trade supporting it. In reading it, one is struck by its raw emotion as much as by its strong reasoning." Smith argued that the book was a turning-point for the slave trade abolition movement and made the case "unanswerably, and I should have thought, irresistibly" and became a supporter of the Society for the Abolition of the Slave Trade, an organisation established by Clarkson, William Dillwyn and Granville Sharp.
Smith became one of a small group of MPs brave enough to support William Wilberforce in the slave trade debate in 1790. Later that year he lost his seat at Sudbury, but the following January he was elected as M.P. for Camelford. Smith joined the Clapham Set, a group of evangelical members of the Anglican Church, centered around Henry Venn, rector of Clapham Church in London.
In 1792 Smith, an active member of the Unitarian Society, became one of the founding members of the Friends of the People Society. In April 1791 he publicly supported the French Revolution. In 1792 he arranged several meetings between William Pitt and Hugues-Bernard Maret, the French foreign minister, in an attempt to avoid war.
William Smith continued to campaign against the slave-trade. One of the major problems facing Smith and his friends was that the slave-trade was highly profitable. As one historian has pointed out: "In one recent study of the Liverpool slave trade the profits in 74 voyages averaged 10.5% at a time when yields on consols (consolidated stocks) were 3 per cent. It was a risky business, and returns fluctured wildly but enough voyages realised 20 to 50 percent to dazzle the investing public."
In 1802 Smith decided to stand for Norwich, which was known for being a gathering place for dissenters and radicals. After the passing of the Abolition of the Slave Trade Act in 1807 Smith joined Thomas Clarkson and Thomas Fowell Buxton to form the Society for the Mitigation and Gradual Abolition of Slavery in 1823. In 1830 the society adopted a policy of immediate emancipation. However, Smith had to wait until 1833 before Parliament passed the Slavery Abolition Act that gave all slaves in the British Empire their freedom.
William Smith died in London on 31st May 1835.
William Wilberforce, the most celebrated campaigner against the slave trade, was also implicated in slavery and the trade, according to a forthcoming book about him and the Clapham sect, written, it so happens, by me. Having given 20 years of his life to the struggle, after the Abolition Act was passed in 1807, he allowed the abolitionist colony of Sierra Leone, which the Clapham sect managed, to use slave labour and buy and sell slaves.