Officers are appealing for information and witnesses following an affray in Borehamwood.
The incident happened just after midnight in the early hours of Saturday, September 10.
At around 12.30am, several males were involved in an altercation in Drayton Road, by the junction with Shenley Road.
A 22 year old man has been arrested on suspicion of affray, possession of an offensive weapon (a pole) and possession of a class B drug (cannabis).He has been released under investigation while enquiries continue.
Detective Constable Helen Osborne, who is investigating, said: “I am appealing for anybody who was in the in the area and saw what happened to get in touch. Any information you have, no matter how small it might seem, could be vital.
“I’m also keen to hear from anyone who was driving in the area and has a dash cam fitted to the vehicle. Please check it and make contact if you spot something that might help.