47 year old Joanne Vickery was found to have breached the policing standards of professional behaviour.
The court heard how the woman had been taken into custody after being arrested on suspicion of being drunk and disorderly.
After being detained, she assaulted Vickery through a cell door before the officer in turn went into her cell and launched an assault.
The incident was captured on CCTV and was reported after staff spotted it while downloading footage for another matter.
The force says “even though Vickery was assaulted first, her behaviour, which amounted to a criminal offence, simply cannot be condoned.”