This is shocking moment a prison officer was punched to the floor by a violent inmate - as other prisoners cheer him on.
Dramatic footage shot in a UK prison shows the prisoner burst out of his cell and square up to two guards who raise their fists in a boxing stance.
He lashes out at one of the guards, smashes him in the face and knocks him to the ground.
As excited inmates cheer, other officers - none of whom appear to have any defensive equipment - rush in and eventually restrain the man.
The footage, filmed from a CCTV camera, has only just emerged and appeared on a Facebook page dedicated to the Handsworth area of Birmingham.