It happened at about 1pm when the driver of a white Citroen Berlingo car pulled in front of the victim’s car. The driver of the Citroen got out and approached the car he had pulled in front of, subjecting the man inside to a tirade of abuse and threats.
The victim was not injured during the incident.
The offender is described as a white man, around 5ft 11ins tall, about thirty-years-old, of slim build and had brown hair which was gelled and stubble on his face. He was wearing a grey zip up jumper, with a white T-shirt underneath and light greyish trousers.
Investigating officer PC Matthew Lynch, based at Slough police station, said: “We are appealing for witnesses to this incident which happened in the middle of the day on a busy stretch of road.
“If you witnessed this incident or have dash-cam footage of the incident, we would ask you to please get in touch.”
Anyone with information should report online, call 101 quoting reference 43200274381, or call Crimestoppers anonymously on 0800 555 111.