Her Majesty's Prison Leeds for the Super Gifted. One of the biggest prisons reserved for Supers in the entire world. It also happens to be the most secured next to the Super Maximum Prison in Russia.
HM Prison Leeds house some of the most heinous villains in the entire world, or the most insane– there really was no distinction between the two in terms of treatment.
There was supposed to be a lot of processes for one to be taken here, but considering the gravity of the individual they were bringing in– almost every procedure was skipped.
Of course, this might seem over the top for someone only considered to be a suspect. But considering Riley Ross was being suspected as Darkday, the most heinous terrorist and villain the world has ever known, this could actually be considered as mellow. If he wasn't as young as he was, then everyone would have already attempted to kill him.
Of course… that wasn't also wise considering Darkday's abnormal strength.