Britain congratulated itself on having made trading in slaves illegal with the 1807 Act. While later legislation ostensibly strengthened the original Act’s provisions, there were persistent allegations, supported by evidence from the British Foreign and Anti-Slavery society among others, that British companies still profited from it. One of the few prosecutions against the owner of one such company, Pedro Zulueta, ended in his acquittal despite evidence to the contrary. The exploration of the economic, political and social factors underlying both trial and acquittal sheds light on the nineteenth-century British economy’s continuing semi-covert involvement in the trade.