Mark was born in Kensal Rise, London to Grenadian immigrant parents, and grew up in Shepherd's Bush. She had her introduction to the music business initially by working as guest vocalist on Dennis Bovell's Sufferer sound system, followed by a residency at the Metro club in Westbourne Park, and via "Star Search" talent contests held at the Four Aces club in Dalston, where she won for ten consecutive weeks. Sound-system operator and record producer Lloyd Coxsone provided dub plates for the contestants to sing over at the contests and, in late 1974, provided the fifteen-year-old Mark with her first recording session, at Gooseberry Studios, where she recorded a cover version of Robert Parker's "Caught You in a Lie", on which she was backed by Matumbi, the single also being released in Jamaica by Gussie Clarke. "Caught You in a Lie" is considered the first lovers rock single. It gave her an instant hit with reggae audiences, and was followed by a version of The Beatles' "All My Loving". Her career was interrupted after a dispute with Coxsone and she concentrated on finishing her studies.