Miles achieved great success at an early age, winning his first significant title as the World Junior Champion in 1974. He also won the British Championship in 1982 and 1985, and he competed in 15 Chess Olympiads from 1974 to 1996. Miles received a silver medal on three occasions.
Miles was very well known for his use of unorthodox, unconventional openings, often playing moves and combinations that were considered dubious or suspect by chess standards. Despite this, his original, innovative play led him to numerous victories against world-class players.
Miles was also known for his computer work in the field of chess. He worked to develop computer programs to play and learn chess, and took part in multiple computer vs. human matches.
His health declined during the latter part of his career, with diabetes-related issues impacting his performance. He had a brief spurt of better health in mid-2001, during which he played in a number of tournaments and attained his highest-ever rating, but he died of heart failure in November that year.
Despite passing away at a relatively young age, Miles maintained a chess legacy in England. He played an integral role in England's growth into one of the world's top chess nations, and his unconventional approaches to the game remain the subject of study among aspiring chess players worldwide.