Tolley This is all based on hearsay, etc. but I think that they just wanted the employer to put pressure on the employee to stop sending £1k a month to their kid, which is allegedly being used to fund a drugs addiction. I'm not 100% sure that they knew/thought that a crime had been committed, until they told the Sun about things.
As an aside, it seems a bit of a strange legal position that you can legally have sex with someone who's 17 yr, which they are old enough to consent to, but they are not legally old enough to consent to explicit photos being taken, even if they fully consent to it and they aren't for publication.