James Marriott was born on 29 October 1730. In June 1746 he was sent to Trinity Hall, Cambridge, and graduated in 1751. Although he had wanted a job in the church, he decided to switch to law in 1755, maybe because his stepfather, a very good lawyer, told him to. He spent three years as librarian to the Duke of Newcastle. He joined the College of Advocates and began his legal job in which he wrote two books on law.