The victim – now an adult – broke down in tears when he spotted the paedo pensioner and told prison officers he was abused by him as a youngster in the 1970s.
Cooper was hauled back before the courts and found guilty of more historic offences against the man, who was himself locked up for raping a young girl.
He has been given a further eight years in jail to run alongside his existing 18-year sentence after being
guilty of three counts of indecent assault and one count of gross indecency with a child.
Manchester Crown Court was told Cooper, previously known as Alan Makinson, is in poor health and could die behind bars.
‘HE STOLE MY CHILDHOOD’
Jurors were told the victim “felt like a child and went back to his cell and broke down crying” when he realised he was in the same jail as his abuser.
In a statement read by prosecutor David Bentley, Cooper’s latest victim said: “I know he stole my childhood. It has destroyed my life.
“If a convicted sex offender can open up about my past abuse, I hope it can help others come forward.
“Some people have the theory that the abused becomes an abuser.
“And in some cases, they might be right.”
Cooper now has a vile roll sheet of more than 50 sexual offences against children committed between the 1970s and 2000s.
The monster would lure his vulnerable victims with money and gifts and force some to eat raw meat from pigs’ heads when they tried to escape his evil clutches.
He was jailed for three years in 1986 after admitting a string of child sex crimes, including rape, but changed his name when released and continued to prey on youngsters.
At his sentencing this week, Judge Timothy Smith explained he was constrained due to the most recent offences being charged under the laws applicable in the 1970s.
He told Cooper: “You are a compulsive, manipulative and predatory paedophile.”
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After the hearing, Detective Constable Joanna Gordon, of GMP’s Public Protection Investigation Unit, said: “Colin Cooper took advantage of a young child to satisfy his own depraved desires and prison is where he belongs.
“I hope that today’s result sends a clear message to victims of historic sexual abuse- no matter how much time has passed – we will do everything in our power to bring perpetrators to justice for these horrific crimes.
“Victims have to live with the trauma of these crimes for a large part of their life and I’d encourage anyone who has suffered previously to please come forward and get the support they need.”