James Aaron Diamond (28 September 1951 – 8 October 2015) was a Scottish singer-songwriter, best known for his three Top 5 hits: "I Won't Let You Down" (1982), as the lead singer of PhD; and his solo performances "I Should Have Known Better", a United Kingdom No. 1 in 1984, and "Hi Ho Silver", the theme song from Boon, which reached No. 5 in the UK Singles Chart in 1986.