An inmate punched a prison officer in the face after he was challenged for leaving his cell in a dressing gown and flip-flops.
Serving prisoner Jamie Richards, 29, had planned to go to collect medication when a warder saw what he was wearing and stopped him on September 30 last year.
Richards told the prison officer he would “knock him out” and later that day he punched the officer in the face as he spoke to another prisoner.
The prison officer hit his head as he fell and suffered a double fracture to his cheekbone, resulting in an extended period off work from high-security HMP Whitemoor in Cambridgeshire.
Richards pleaded guilty at Cambridge Crown Court to assault occasioning grievous bodily harm (GBH) without intent, Cambridgeshire Police said.
The force said he was sentenced on Monday to a further two years in prison after he finishes serving his current sentence.
At the time of the assault Richards was serving an 11-year prison sentence for an attempted robbery in Swansea in 2016 and further offending while behind bars.
Richards was sentenced at Swansea Crown Court after holding a kitchen knife to the throat of a woman in her own house and knifing her pet dog in the stomach.
He wrote social media messages while at large – including threats against the family of his victim that “snitches get stitches” – before handing himself in after a month on the run.
Richards, then of Gerald Street, Hafod, Swansea, had dozens of previous offences on his record and was at that point sentenced to a total of nine and a half years in prison.
