This shocking footage shows the moment prisoners brawled behind bars at HMP Featherstone.
The images, taken on a smuggled mobile phone at the Staffordshire jail, appear to show inmates having their hands bound with material ahead of the organised fight.
A group of around 20 men can be seen standing around, some on mobile phones before the violence starts.
The footage ends when when of the fighters is knocked to the floor, before he is repeatedly punched by his opponent.
The images have been reported to police, and anyone involved faces disciplinary action and the prospect of more time behind bars.
Today, a Prison Service spokesperson told the Express & Star: "This behaviour is completely unacceptable and we are working to remove the content from social media.
"We are committed to making prisons places of safety and reform and are stepping up measures to tackle violence and find and block mobile phones in prisons."
They were arrested at the prison after members of the West Midlands regional organised crime unit and HMP Oakwood’s security team swooped.
The two arrests were made around 9am on Friday, January 27.Subscribe to our Newsletter