Slavery was finally outlawed in the British colonies in 1833. Worldwide emancipation then became the abolitionists' new goal. The British and Foreign Anti-Slavery Society (BFASS) was founded and plans made for the World's Anti-Slavery Convention, to be held in London in June 1840. With over 500 delegates invited from all over the globe, the twelve-day convention was to hear reports from countries where slavery still existed and from British colonies where it had ended.

The Society's belief in the importance of this international meeting led to the commission of a commemorative painting. They probably chose Haydon because he had experience in the production of such large group portraits. In 1820, he had exhibited a huge canvas entitled Christ's Entry into Jerusalem, including likenesses of Keats and Wordsworth. From 1832-4 he had also painted the celebration banquet for the passing of the Great Reform Act. (1832-4) At first Haydon was unwilling to accept the commission. He did not care for the BFASS mission and doubted whether the convention would make a visually exciting scene. Despite these reservations, he attended the first day of the conference at which Thomas Clarkson, Irish radical Daniel O'Connell and Henry Beckford, a freed slave, all spoke. Overwhelmed by the emotion of the assembly, Haydon began to sketch the scene, remarking in his diary soon after that it had affected him deeply.