The sick scheme was exposed in a leak of 40Gb of video footage which was smuggled out of the archives of Russia's FSIN prison service by an anonymous Belarussian man who claims he was tasked with archiving the videos while in jail.

Now freed, the man handed a smuggled copy of the material to campaigners at Gulagu.net who have published parts of it online - while calling for reforms. MailOnline has reviewed a section of the material, but has decided not to publish most of it because of the highly distressing nature of the footage.