Watkins was jailed in December 2013 for 13 child sex offences, including the attempted rape of a baby.
The sentencing judge at the time, Mr Justice Royce, said the case broke “new ground” and “plunged into new depths of depravity”.
Watkins was also condemned for showing no remorse for his actions and it was later revealed he had spoken to a female fan from prison about his sex offences, describing them as “mega lolz”
The attack on Watkins occurred at HMP Wakefield, which is known as Monster Mansion because of the large number of very dangerous and serious criminals housed there.
In 2005, Ian Huntley, the Soham murderer, was scalded with boiling water by serial killer Mark Hobson, who was already serving a whole life tariff.
In 2013 Mark Bridger, who abducted and murdered April Jones, was slashed across the face by fellow inmate Juvinal Ferreira.
The wound was so deep it severed an artery in Bridger’s head and he required emergency surgery to save his life.
Ferreira, a convicted rapist and killer, claimed he had attacked Bridger in an attempt to get him to reveal where he had hidden April’s remains.
He had his life sentence doubled for the attack.