In 1740, Mores's father died leaving a considerable inheritance, and later the same year he entered the Merchant Taylors' School in London.
[1] He published his first work, Nomina et insignia gentilitia nobilium equitumque sub Edoardo primo rege militantium (a study of the heraldry of the knights of Edward I), in 1749, at the age of 19 and when he was still at Oxford.
In 1754–55 he assisted his friend Andrew Ducarel (who had limited eyesight) in compiling a manuscript history of Croydon Palace and the town of Croydon for presentation to Thomas Herring, Archbishop of Canterbury: however, the work led to a virulent rift between the two when Mores discovered that he was not given due credit on the title page.
[1][2] After James Dodson's death, Mores became the leader of the group which eventually became the Society for Equitable Assurances on Lives and Survivorship in 1762.
The couple had two children: a daughter, Sarah, who predeceased her father; and a son, Edward Rowe (1757 - 1846) who was an active magistrate, and deputy Lieutenant for the counties of Middlesex and Essex.