Lee was Kelly's fiancé. They were together for sometime until Kelly punched Lee in the face after hearing his less-than-romantic thoughts. He announced that their relationship was over and fled from the apartment.
In Episode 4 (Series 1), it is revealed that Lee proposed to Kelly after a party at the nightclub. Upon leaving the club, Lee broke into a nearby car, in which he found an engagement ring. He proposed to Kelly right there, and drove off in the stolen vehicle. It is later revealed that the car belonged to Tony and the ring was intended for Sally.