50.Section 24 provides A with a defence to abuse of position of trust offences if he can prove that his sexual relationship with B pre-dated his relationship of trust with B. So if A could prove that he and B had a sexual relationship before A went to work at the school at which B is a pupil, he would not commit an offence by continuing that sexual relationship. The effect of subsection (2) is to limit this to the situation where the sexual relationship that pre-dated the relationship of trust was lawful, so it would not cover for example a relationship with a child of under 16.