Conduct by a person (A) which would otherwise be an offence under any of sections 38 to 41 against another person (B) is not an offence under that section if, immediately before A became involved in B's care in a way that falls within section 42, a sexual relationship existed between A and B.
Subsection (1) does not apply if at that time sexual intercourse between A and B would have been unlawful.
In proceedings for an offence under any of sections 38 to 41 it is for the defendant to prove that such a relationship existed at that time.