I think he was making the distinction between say someone being attacked and raped and a young couple where one was over 16 and the partner under 16 having consensual sex. If a boy of 17 or 18 is going out with a girl of 14 or 15 and they have sex in which both are agreed, the boy can still be charged with rape. I think that there should be a distinction in that case and that is what Ken Clarke is saying, although he didn't put it very well.