By Candice Carty-Williams

"There is only one way to leave this place … the cemetery." That's what you're letting yourself in for with Russia's Toughest Prisons. Three of Russia's most guarded institutions, which confine "maniacs, paedophiles and terrorists", open their doors for the first time, allowing us into the minds of the criminals, as well as revealing the strictly regimented routines carried out by guards in order to protect the inmates from each other, and themselves.