30.—(1) Conduct by a person (A) which would otherwise be an offence under any of Articles 23 to 26 against another person (B) is not an offence under that Article if at the time—
(a)B is 16 or over, and
(b)A and B are lawfully married or civil partners of each other.
(2) In proceedings for such an offence it is for the defendant to prove that A and B were at the time lawfully married or civil partners of each other.