Gareth Benjamin Davies, 27, was sentenced in the ACT Supreme Court on Wednesday after pleading guilty to recklessly inflicting grievous bodily harm and two charges of aggravated robbery.

The court heard Davies was on remand in the Alexander Maconochie Centre on the robbery charges when he king hit the man earlier this year.

The 60-year-old paedophile, who was under strict protection at the time of the assault, lost an eye as a result of the attack.

An earlier sentencing hearing was told that Davies came into contact with the normally segregated prisoners due to a failure by prison authorities to separate at-risk and general detainees.

A pre-sentence report said Davies had tried to minimise his responsibility for the attack by blaming Corrections for not keeping him and the victim apart, stating that he had been molested as a child, and claiming he could not remember the incident. But Justice John Burns cast doubt on the explanations and labelled the assault a ''significant act of violence''.

''You have a propensity to violence which is unacceptable,'' Justice Burns said. The court also heard Davies had been assessed as a high risk of reoffending and had a history of being disruptive and threatening violence against other inmates and prisoner guards while in custody.

But the court also heard Davies had expressed remorse for the aggravated robbery and engaged with a number of rehabilitation programs at the jail.

Justice Burns sentenced Davies to six years and seven months in jail. The sentence was backdated to take into account time Davies had spent in custody, with a non-parole period of four years.