Hertfordshire Constabulary is calling for witnesses after a man driving a white van got out of his vehicle and got in an argument with a woman in her fifties, who was walking down Clarendon Road.
The incident is believed to have happened between 5.30pm and 6pm on Monday, July 14.
The woman then walked away before the man got back into his van and followed alongside the woman, while the pair continued their argument.
Both parties then went into Watford police station.
PC Robert Rawlings is investigating and said: "This incident happened during a busy period of the day and it is believed there were a number of people around, including taxi drivers and pedestrians, who may have witnessed what happened.
"If you remember seeing a white van being driven alongside a woman and/or overheard what was said between the pair please contact me straight away."
Anyone with any information in relation to this incident can telephone PC Rawlings via Hertfordshire Constabulary’s non-emergency number 101, quoting reference C1/14/3260.