Frank Wilson. He wrote and produced hits for the Supremes and Marvin Gaye. In 1965 he stepped into the booth himself and cut Do I Love You -- a record so explosive, so urgent, that Berry Gordy told him to focus on producing instead. The copies were destroyed. All except one. That one surviving 45 became the holy grail of Northern soul -- the most expensive 7-inch single ever sold, north of £100,000. The song that wasn't supposed to exist outlasted everything.