A police officer is in hospital with serious facial injuries after being attacked at the Picton police station.
The officer had arrested a man for disorderly behaviour on Thursday and had just un-handcuffed him in the cells when attacked about 9.15am.
The officer was pushed to the ground and punched repeatedly in the face.
The attack was stopped by the female civilian watchhouse keeper and an off-duty police officer.
The man appeared at the Blenheim District Court on Thursday afternoon charged with wounding with intent to injure.
Marlborough area commander Inspector Ross Grantham said the incident should act as a warning to others in the police force.
"All our police officers are taught as part of their staff safety training how to deal with these people.
And at times such as this, we don't react quick enough and we're over-powered.
"So it's a matter of just reminding police officers about maintaining your own safety and the safety of the public."
Mr Grantham also praised the actions of the people who came to the officer's aid.