Couple of points here from the BBC story.
The step-father is quoted in the article as saying allegations were put to the BBC "for an hour", appearing to contradict a previous statement in Monday's edition which stated: "The family say no-one from the corporation rang them for a proper interview after the initial complaint."
The article also reports that the step-father went to the police about the matter but was told "they couldn't do anything as they said it wasn't illegal."
It's possible they got an overworked desk sergeant who didn't know the law, but it's also possible that The Sun added "started at 17".
People tell me there are some well-known sites where people sell, er, pictures, directly to punters. Is that's what happened here initially, I wonder?