Henry Venn (1725 – 1797) and his son John Venn (March 9, 1759 – July 1, 1813), were central figures in the anti-slavery movement later to become known as the Clapham Sect which was based around the nearby Holy Trinity Church, on Clapham North Side, where William Wilberforce used to worship. Shortly after studying at Cambridge Henry took holy orders and within a few years came to London becoming curate of Clapham and was also elected lecturer of St Swithin’s, London Stone and St Alban’s Wood Street. It was at Clapham he founded a movement calling for the abolition of slavery and the promotion of missionary work at home and abroad. In 1759 Henry moved to Yorkshire where he continued to work on his evangelical ideas writing The Compleat Duty of Man, published in 1763, and promoting his ideas to local congregations. His son John Venn who was born during his father’s curacy in Clapham, followed his father to Cambridge and the priesthood, becoming rector of Clapham from 1792 until his death. During his time there he espoused his father’s ideas which brought him into contact with Wilberforce, Henry Thornton, James Stephen, Zachary Macaulay, and others. Many were members of Parliament, where, in addition to their abolitionism, they worked for prison reform, prevention of cruel sports, and the suspension of the game laws and the lottery. Venn was the father of Henry Venn (1796 – 1873), honorary secretary of the Church Missionary Society, and grandfather of logician and philosopher John Venn, who created the Venn diagram.