"Recently" as in 2015, in fact, the last government not this one.
It was due to take effect as a law next week, but it's been delayed for unknown length.
It's a stupid idea that has very little public support, but that's Theresa May all over (she was Home secretary - whose purview such a law falls under - at the time it was made a law, before becoming PM)
These hits could include a grown adult looking at an adult model's pics on twitter, on their own phone, in their own time.