A Channings Wood prisoner attacked a warder and left him with a broken nose after a visiting time bust-up.
Daniel Kennedy had been sent to the jail at Denbury, near Newton Abbot, for a 'Thinking Skills' course to prepare him for his release but became angry when his girlfriend complained at the way she had been treated.
He got up from the visiting table after a short exchange of words with Prison Officer Michael Doyle and then attacked him with a blow to his face, Exeter Crown Court was told.
Kennedy, aged 31, had been due for release within days but has instead been recalled to serve the whole of his three-year sentence for robbery.
The prisoner, who is currently at Whitemoor high security jail in Cambridgeshire, admitted causing actual bodily harm and was jailed for seven months by Judge Phillip Wassall.
The sentence will be served alongside his existing term and will to change his current proposed release date of April 2015.
The judge told him:"You took umbrage at the officer and hit him in the face. This happened in a prison environment and was a direct challenge to the officer's authority in the visiting suite with other people there."
Mr James Taghdissian, prosecuting, said Kennedy was an inmate at Channings Wood in May last year when he was being visited by his partner and their small child.
He said:"His girlfriend was allocated to a table in the visiting hall and it seems she was not happy at the way prison staff had treated her and told this to Kennedy.
"He stood up and PO Doyle went to speak to him. There is a dispute about the language used but the officer says he asked him to sit down.
"Kennedy punched the officer to the face, causing a fractured nose and a considerable amount of pain. He declined to have an operation to straighten the nose because there was no guarantee of success.
"The defendant said the officer had been rude to him in relation to issues with his girlfriend.
"We say there are aggravating features. The location in the visiting hall, the fact he is a serving prisoner, and the presence of other people including prisoner, visitors and children.
"This was a vulnerable situation for prison staff and this offence was committed against a person who was serving the public."
Mr Niall Brooks, defending, said there had been tension between Kennedy and the officer before the incident.
He said he had been at the jail to complete a pre-release Thinking Skills course and as a result of it had not been able to complete it and had instead been recalled to serve his full sentence and moved to higher category prisons.
He had also spent three months in segregation and been banned from receiving visits from his partner and daughter for six months.
He has developed Crohn's Disease while serving his sentence and needed hospital treatment shortly before his last scheduled court appearance.
He said he now wants to finish his sentence and retrain as a youth worker so he can discourage others from following the same course as he has.
