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.
Legal Source
Sexual Offences Act 2003, Section 1.
Observations
In Scotland, the legal provision for rape can be found in the Sexual Offences (Scotland) Act 2009.