Thames Valley Police is appealing for witnesses following an assault near Olney.
Between 5pm and 6pm on Wednesday 31 March the victim, a 61-year-old man, was driving along the B565 when he stopped at a junction and a man in a vehicle behind him started shouting at the victim.
The victim continued on his journey and later arrived at his property in Bedford Road, Cold Brayfield to find the same man parked at the end of his drive.
The offender got out of his vehicle and approached the victim, grabbing his mobile phone and keys, which he subsequently threw into the nearby bushes. He then punched the victim in the face.
The victim sustained cuts and bruising to his face, but did not require hospital treatment.
The offender is described as a white man, in his early thirties, around 5ft 5ins tall with short hair and a medium length ginger beard. He has tattoos on his arms and left hand. He is believed to have been driving a small blue van, possibly a Vauxhall combi van.
Investigating officer PC Jamie March, based at Milton Keynes police station, said: “I am appealing to anyone who believes they have information about this incident or recognises the descriptions above to please contact the police.
“I would also ask anybody in the area to please check dash-cam or doorbell footage and call us if it has picked up anything that could assist this investigation.
“You can contact us online or by calling 101, quoting reference number 43210136115.
“Alternatively, for 100% anonymity, you can also call the independent charity Crimestoppers on 0800 555 111.”