A taxi driver in Milton Keynes was the victim of a vicious attack before his car was taken on Sunday night.
Police are appealing for witnesses after the robbery, which occured around 9.40pm.
The victim, a 49-year-old taxi driver, was threatened with a large knife which the offender had in a bag in the back of the vehicle.
The knife was then jabbed towards the victim and he was punched in the head before being told to hand over the keys to his silver Seat Alhambra.
After being dragged from the car, the victim was kicked in the calf which caused him to fall to the floor and he lost consciousness before waking up in an ambulance.
The offender then got in the vehicle and drove it away from Walton Road, Caldecotte. He was last seen driving in the direction of Heybridge Crescent.
The victim was left bleeding from the mouth, and had bruising and reddening to his right temple and a graze to his left palm. He was taken to Milton Keynes General Hospital.
The offender is described as a white man with an English accent, approximately 5ft7ins tall with short hair and slim build. He was dressed in a white short-sleeve t-shirt, with a black jumper and dark tracksuit bottoms and was carrying a black laptop bag.
Investigating officer detective constable John Swallow said: “This was a vicious attack on a man in a public area.
“The victim was left with memory loss and felt very disorientated.
“I am appealing for anyone who may have seen the incident to come forward.”
If you have any information relating to this case, call 101 quoting reference '43180167671', or contact Crimestoppers anonymously.