Rape
(1) A person (A) commits an offence if-
(a) he intentionally penetrates the vagina, anus or mouth of another person (B) with his penis,
(b) B does not consent to the penetration, and
(c) A does not reasonably believe that B consents.
(2) Whether a belief is reasonable is to be determined having regard to all the circumstances, including any steps A has taken to ascertain whether B consents.
(3) Sections 75 and 76 apply to an offence under this section.
(4) A person guilty of an offence under this section is liable, on conviction on indictment, to imprisonment for life.'
A strap on would not be a penis, it would still be some sort of sexual assault. In America a woman can be charged with raping a man. Lots of things other than sexual arousal could cause an erection, I would have thought that maybe using viagra to drug a man might cause the laws to change.