Hartley was born in Smallfield, England, near Crawley, and was a childhood friend of future bandmate Simon Gallup.
[2] Near the end of 1979, The Cure needed a new bassist following the departure of founding member Michael Dempsey, and recruited Gallup for the position.
[3] Gallup suggested adding Hartley as the band's first full-time keyboardist to broaden their sound.
[4] Hartley was a full member of the Cure for their 1980 album Seventeen Seconds and the ensuing tour.
[3][6] After leaving the Cure, Hartley remained friends with Gallup and was an early member of the band that became Fools Dance.