Most black slaves in England had been brought back by sea captains. Their status was legally uncertain. Some had been legally emancipated. Francis Barber had been freed by his previous owner, Colonel Bathurst; similarly a black valet in the service of Sir Joshua Reynolds. But slaves were often put up for public sale in Bristol and Liverpool.
Granville Sharp, then a junior clerk in the Ordinance Office (grandson of an Archbishop of York) took up the case of James Somerset, who had been brought to England by his master, Charles Stewart of Boston, in 1769. He escaped in 1771, was recaptured, then put on board the Ann and Mary, whose captain was John Knowles, bound for Jamaica, where he was to be sold.
The case came between Lord Chief Justice Mansfield on the Court of Kings Bench. Mansfield decided that there was no legal definition as to whether there could or could not be slaves in England. After procrastination, he decided the case on the ground that slavery was so odious that nothing could be suffered to support it. Somerset therefore was freed. There was general rejoicing among the many blacks present at the hearing. However in 1779 Mansfield stated that his judgment went no further than to determine that the master had no right to compel the slave to go into a foreign country. Little changed in the Caribbean and Africa, yet the judgment profoundly affected public opinion