Paul Wadkin, 33, and Jason Gomez, 45, lured Darren Flynn into a cell before stabbing him at least 190 times with two makeshift weapons.
Gomez and Wadkin stabbed their victim 190 times and then openly bragged to prison officers that they were responsible.
"It was a carefully planned attack with one intention, to commit murder.
"Their motive was based on the mistaken belief that the victim was a sex offender and 'a grass', of which there is absolutely no evidence of either. "
Neither of these men has showed any remorse for their horrific actions and instead they smiled and laughed in court as the judge was passing sentence."