Marzin Moshen, 20, and Finley Phillips, 19, were caught on camera turning on Ryan Young when he tried to intervene to break up a fight at a prison.

Mr Young, who worked at HMP Parc in Bridgend, South Wales, told Sky News he was "just doing what [he] was trained to do".

"I worked there for over 20 years, so your training kicks in then, your knowledge of working there kicks in," he said.

"So you react to it to try and split up the situation, to de-escalate it by separating the people."

He suffered concussion and had to have stitching above his eye after the incident, footage of which has been released by the Crown Prosecution Service (CPS).

CCTV showed Phillips punching and stamping on Mr Young, before Moshen stamped on him near his head while he was incapacitated.

"I had concussion for quite a long time after it, and then I have to have cognitive therapy for having disturbed sleep," he said.

"PTSD from the situation, which had stopped me from sleeping, affected my moods and stuff."

'Change of pace'

Mr Young said the staff at the prison were like "one big family" and had helped him overcome the incident.

"You wouldn't be able to work unless everybody was so close and supported you and it's from their support that I actually managed to get back to work," he added.

"Because it did affect me for a while and without them I probably wouldn't have got back into work."

Mr Young, who will soon start a new profession as a train conductor, said he hopes for a "complete change of pace" as he embarks on his new career path.

"Now I am having a career change and this incident is one of the reasons, not the entire reason, but one of the reasons which has made me look at having a career change as well," he said.

"Hopefully a bit more of a relaxed environment, not as much confrontation."

The judge told the defendants at the sentencing hearing it was "clear Mr Young was not the target of [their] violence".

"But there is a harrowing image of him on the CCTV lying motionless on the floor," he added.

"He was simply trying to do his duty in a very difficult public service."

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Moshen pleaded guilty to assault occasioning actual bodily harm and was sent to a young offenders' institution for five months.

Phillips admitted wounding and was sentenced to 16 months at a young offenders' institution.