A DOUBLE rapist who slashed serial killer Peter Tobin attacked another fellow sex offender behind bars.

Sean Moynihan, 31, hit Ernest Radic from behind with a metal bar in the Barlinnnie prison gym in December 2014.

Radic - a Hungarian from Slovakia who repeatedly raped a woman and filmed it on his phone - had earlier assaulted Moynihan when they were both inmates at Glenochil prison, it was claimed.

Convicted sex offender Moynihan, who will be sentenced later this month for slashing notorious serial killer Tobin in prison, admitted the assault at Glasgow Sheriff Court.

Sheriff Charlotte Coutts sentenced the rapist to six months in prison to be served alongside his current time inside.

The court heard Moynihan and Radic were both in the gym at Barlinnie around 9am on December 1 2014 when Moynihan hit him on the back with his weight bar.

It was heard Radic fell to the ground and Moynihan put the bar down and walked away leaving his victim passed out.

He came to a short time later after staff had been made aware of the incident.

Moynihan admitted to staff that he "done him in" using the bar in the gym

Radic, who was jailed for six years in 2013 for his offences was taken to hospital and given a CT scan but later discharged with pain killers.

Defence lawyer Charlie McCusker said that previously when both men were inmates at Glenochil prison Radic assaulted his client.

He said that after the assault carried out by Moynihan, he was put in segregation for a period of time.

Last month the convicted rapist admitted assaulting a sleeping Tobin in Saughton Prison, Edinburgh, by hitting him on the head with a razor.

Moynihan is also still to be sentenced for raping a teenager at knifepoint on a cycle path last year in Johnstone

Moynihan was jailed in 2009 for raping a 16-year-old girl.