Reynolds, who’s now serving time at HMP Bullingdon, was found guilty on Wednesday following a five-day trial, having denied charges of grievous bodily harm with intent, two counts of rape and a sexual assault.
Police described the victim, who has since been released from prison, as “vulnerable” and said he is still affected both physically and mentally by the attack.
Detective Sergeant Harry Wilson said: “This was a horrific attack on a vulnerable man in a prison.”
“While the victim has since left prison, he continues to deal with the physical and mental impact of what happened to him.
“This was a difficult and long investigation, and I hope this shows that we will work closely with the prison to investigate any criminal offences that occur there.”