http://www.legislation.gov.uk/ukpga/2003/42/part/1/crossheading/rape/section/1

This definition concerns penetration (penile emphasis) to the exclusion of envelopment (vaginal emphasis)

This breaks the Equality Act 2010, by indirect discrimination

https://www.gov.uk/guidance/equality-act-2010-guidance

Rape is “Forced to have sex against their will” yet a form of this is classed only as sexual assault, carrying a lesser sentence.

http://www.legislation.gov.uk/ukpga/2003/42/part/1