It is not rape - it is unlawful sexual intercourse. Kenneth Clarke was wrong - he was referring to the statutory rape of the USA.
Interesting reading here:
http://www.cps.gov.uk...l_sexual_intercourse/
Especially:
"Even if the defendant is over 24, a prosecution may not be in the public interest if he had reasonable cause for believing that the girl was over 16.
The following factors will also be relevant:
the relevant ages of the parties;
the emotional maturity of the girl and whether she entered into a sexual relationship willingly;
the relationship between the parties and whether there was an existence of a duty of care or breach of trust (refer to the section on Abuse of Trust in Sexual Offences Act 2003, elsewhere in Legal Guidance)."
So, this man reasonably believed her to be over 16 and was not in a position of trust. The girl was willing and lied about her age.
Not rape.