James "Jim" Diamond (born 28 September 1953, Glasgow) is a Scottish singer-songwriter, best known for his three Top 5 hits. The first was "I Won't Let You Down" (1982), as the lead singer in the trio PhD, with Tony Hymas and Simon Phillips. His solo performance, "I Should Have Known Better", was a United Kingdom number one in 1984. The third track was the theme song from Boon, ... Show More