Somerset (P), a slave, was purchased by Charles Stewart (D), a customs officer and an inhabitant of Virginia, when he was in Boston, Province of Massachusetts Bay, a British crown colony in North America. D brought P with him when he returned to England in 1769, but P escaped. When recaptured D had him imprisoned on the ship Ann and Mary (under Captain John Knowles). The purpose was to sell P in Jamaica. P made an application for a writ of habeas corpus. Knowles produced P, and a hearing was ordered. The case was eventually heard in February 1772. P's advocates argued that while colonial laws might permit slavery, neither the common law of England nor any law made by Parliament recognized the existence of slavery and slavery was therefore unlawful. D argued that property was paramount and that it would be dangerous to free all the black people in England, who numbered at the time approximately 15,000.