(1) If in proceedings for an offence to which this section applies it is proved that the defendant did the relevant act and that any of the circumstances specified in subsection (2) existed, it is to be conclusively presumed—
(a) that the complainant did not consent to the relevant act, and
(b) that the defendant did not believe that the complainant consented to the relevant act.
(2) The circumstances are that—
(a) the defendant intentionally deceived the complainant as to the nature or purpose of the relevant act;
(b) the defendant intentionally induced the complainant to consent to the relevant act by impersonating a person known personally to the complainant.