He was the son of James Park, a surgeon from Edinburgh, and was brought up in Edinburgh until his father's practice moved to Surrey. He was educated first at Northampton Grammar School and then at Lincoln's Inn. He was called to the bar on 18 June 1784 and in 1787 published a successful Treatise on the Law of Marine Insurance, which was reprinted six times during his life. That book drew much on the cases of Lord Mansfield. It brought him a good practice. As an advocate, he made more of a reputation for care than for eloquence.
