George Thompson was a veteran anti-slavery activist who had played a role in campaigning to outlaw slavery in Britain and throughout its Empire in the early 1830s. In the same period he became close friends with American abolitionist William Lloyd Garrison, and began writing articles for his newspaper, The Liberator. Thompson also travelled to the United States to protest against pro-slavery legislation, such as the Fugitive Slave Law of 1850, and became heavily interested in the buildup towards Southern secession.
When war commenced, he formed the London Emancipation Society, chairing a number of public meetings the organisation held at the Exeter Hall in the Strand and St James’s Church, Piccadilly. He also was a subscriber of The London American. In 1864 Thompson toured the United States, where he was well-received by Northern political leaders, including President Lincoln and Secretary of State William H. Seward.