Clarkson was most famous for his role in the abolition movement, to which he devoted himself entirely, giving up on a career in the church. Over the course of his life, Clarkson would publish 23 pamphlets, most of which dealt with slavery. His very first of these, the 1786 An Essay of the Slavery and Commerce of the Human Species, Particularly the African was instrumental in the recruiting William Wilberforce to the abolitionists’ cause. During the long campaign to end the slave trade, Clarkson rode around England collecting evidence for use in Parliament, traveling an estimated 35,000 miles in all. Though not himself a politician, Clarkson was active in helping Wilberforce present his bill before Parliament.
When the Sierra Leone Company was formed, Clarkson was one of its Directors. He later resigned the position shortly after the dismissal of his brother John as governor of the colony, though he claimed to be motivated by the company’s increasing dependence upon the British government.
Hugh Brogan, ‘Clarkson, Thomas (1760–1846)’, Oxford Dictionary of National Biography, Oxford University Press, 2004; online edn, May 2011, http://www.oxforddnb.com/view/article/5545, accessed 24 April 2012.