A fellow prisoner has admitted trying to kill Soham murderer Ian Huntley.
Damien Fowkes, 35, pleaded guilty at Hull Crown Court to slashing Huntley's throat in Frankland Prison, Durham, in March last year.
Fowkes, from Northampton, also admitted the manslaughter of child killer Colin Hatch, who was strangled at Full Sutton Prison near York in February this year.
He was initially charged with Hatch's murder but his plea of guilty to manslaughter was accepted on the grounds of his diminished responsibility.
The court heard how Fowkes shows "strong psychopathic traits" and was told he attacked Huntley on the healthcare wing at Frankland, where the Soham killer had been working.
Using a home-made weapon, Fowkes slashed Huntley, causing a "severe gaping cut to the left side of his neck". The judge was told the wound was 7in (18cm) long and required 21 stitches.
Fowkes was in prison serving a life sentence for robbery which was handed down in 2002. But the court heard his minimum tariff of five years and 220 days had already expired when he attacked Huntley.
The judge was told he killed Hatch on D Wing at Full Sutton. This is for vulnerable prisoners and Fowkes was there due to self-harming incidents.
Mr Reeds said Fowkes barricaded himself and Hatch into a cell and told prison officers he would not kill him if they stayed outside. The officers dealt with it as a hostage situation.
Mr Reeds said Fowkes said he was motivated to commit both attacks because "they were offenders against children". He said Fowkes remarked: "They just do my head in. It was the same when I did Huntley."