An article from the UK about the historical context of the two-tiered age of consent law (felony under 13, misdemeanour under 16) that was introduced in 1885 (and in a sense remains today) and how modern goals don't really align with the goals posited when that reform was first introduced.
At the time age of consent laws were as much about control (by removing the capacity for legal consent) as they were about protection. One quote on that point is
It's actually interesting that the UK law, with very minor technical adjustment could actually reflect a model similar to 16/12, or at least 16/13. The two tier system already exists in law. Of course the social adjustment required would be very major.The 1885 law on sexual consent meant, to cite the 1908 Royal Commissioners on the Care and Control of the Feeble-Minded, that ‘[t]he power of consenting to unlawful defilement … has been taken from girls under sixteen’.