A man is being treated for a serious head injury after he was hit with a lump of wood by a gang in Cambridge.
The 43-year-old victim was walking down an alleyway between Buchan Street and Banff Close on Thursday evening, when he was struck on the back of the head.
He fell to the floor, where he was hit again with the wood and kicked and punched, police said.
The man managed to walk to a shop for help and was taken Addenbrooke's Hospital.
Police said they were keen to speak to the driver of a dark saloon car who stopped to help the man after the attack.
Det Con Ellie Mansfield said: "This was a vicious attack that left the victim with serious head injuries.
"He was hit with a large lump of wood then punched and kicked while he was on the floor.
"I would appeal to the driver of the car who stopped to help to contact police, he may have vital information to help the investigation."