I would actually photocopy the ID and keep a copy for future reference
Initially the police following their guidelines, then the CPS following theirs, but ultimately it is the courts who decide whether or not an image is indecent.
As said though, by the time you get that far its to late, the damage is already done.
I find it disconcerting that an adult of any age can have sex with a 16 yr old, so see her in the flesh naked, etc etc.
They commit no offence whether they be 16 or 60 yrs old, yet if the same people posses an image of her naked they can be arrested and tried as a paedophile.
Our laws are outdated and an ass, they need updating starting with the age of consent and moving on from there.
If the law gave the age of consent as 14 but with a maximum age gap of 3 yrs between partners until the age of 18 it would make things easier to enforce all round, it would decriminalise teenage sex and could have a clause written in that repealed simple possession of an image for those under 18, distributing would still be an offence.It would then set a clear cut point of 18 for an adult to both sleep with and photograph a younger woman, something that to me seems like common sense whilst also allowing the easier prosecution of those having sex with minors.
We also need the law changing so that the age of responsibility where someone is deemed an adult by the police at the age of 16 in respect to criminal charging etc, equalised with the age of majority (18).
With all these differing ages for different things its a minefield full of loopholes that some exploit and lack of knowledge that leads to some togs ending up in hot water.
Oh and remember the same could apply if you lend your camera to someone and unknown to you illegal material is left on it.